How do visual luminance, shape, motion, and depth bind together in the brain to represent the coh... more How do visual luminance, shape, motion, and depth bind together in the brain to represent the coherent percept of a 3-D object within hundreds of milliseconds (msec)? We provide evidence from simultaneous magnetoencephalographic (MEG) and electroencephalographic (EEG) data that perception of 3-D objects defined by luminance or motion elicits sequential activity in human visual cortices within 500 msec. Following activation of the primary visual cortex around 100 msec, 3-D objects elicited sequential activity with only little overlap (dynamic 3-D shapes: MT-LO-Temp; stationary 3-D shapes: LO-Temp). A delay of 80 msec, both in MEG/EEG responses and in reaction times (RTs), was found when additional motion information was processed. We also found significant positive correlations between RT, and MEG and EEG responses in the right temporal location. After about 400 msec, long-lasting activity was observed in the parietal cortex and concurrently in previously activated regions. Novel tim...
Cortex; a journal devoted to the study of the nervous system and behavior, 2018
The default mode network (DMN) comprises defined brain regions contributing to internally-directe... more The default mode network (DMN) comprises defined brain regions contributing to internally-directed thought processes. Reductions in task-induced deactivation in the DMN have been associated with increasing age and poorer executive task performance, but factors underlying these functional changes remain unclear. We investigated contributions of white matter (WM) microstructure, WM hyperintensities (WMH) and Alzheimer's pathology to age-related alterations in DMN function. Thirty-five cognitively normal older adults and 29 younger adults underwent working memory task fMRI and diffusion tensor imaging. In the older adults, we measured cerebrospinal fluid tau and Aβ (markers of AD pathology), and WMH on FLAIR imaging (marker of cerebrovascular disease). We identified a set of regions showing DMN deactivation and a set of inter-connecting WM tracts (DMN-WM) common to both age groups. There were negative associations between DMN deactivation and task performance in older adults, consi...
Forms of implicit memory, including repetition effects, are preserved relative to explicit memory... more Forms of implicit memory, including repetition effects, are preserved relative to explicit memory in clinical Alzheimer's disease. Consequently, cognitive interventions for persons with Alzheimer's disease have been developed that leverage this fact. However, despite the clinical robustness of behavioral repetition effects, altered neural mechanisms of repetition effects are studied as biomarkers of both clinical Alzheimer's disease and pre-morbid Alzheimer's changes in the brain. We hypothesized that the clinical preservation of behavioral repetition effects results in part from concurrent operation of discrete memory systems. We developed two experiments that included probes of emotional repetition effects differing in that one included an embedded working memory task. We found that neural repetition effects manifested in patients with amnestic mild cognitive impairment, the earliest form of clinical Alzheimer's disease, during emotional working memory tasks, b...
Neurofeedback (NF) is a form of biofeedback that uses real-time (RT) modulation of brain activity... more Neurofeedback (NF) is a form of biofeedback that uses real-time (RT) modulation of brain activity to enhance brain function and behavioral performance. Recent advances in Brain-Computer Interfaces (BCI) and cognitive training (CT) have provided new tools and evidence that NF improves cognitive functions, such as attention and working memory (WM), beyond what is provided by traditional CT. More published studies have demonstrated the efficacy of NF, particularly for treating attention deficit hyperactivity disorder (ADHD) in children. In contrast, there have been fewer studies done in older adults with or without cognitive impairment, with some notable exceptions. The focus of this review is to summarize current success in RT NF training of older brains aiming to match those of younger brains during attention/WM tasks. We also outline potential future advances in RT brainwave-based NF for improving attention training in older populations. The rapid growth in wireless recording of bra...
According to previous literature, trait anxiety is related to the tendency to choose safety optio... more According to previous literature, trait anxiety is related to the tendency to choose safety options during risk decision-making, that is, risk avoidance. In our opinion, anxious people's risk preference might actually reflect their hypersensitivity to emotional information. To examine this hypothesis, a decision-making task that could elicit the framing effect was employed. The framing effect indicates that risk preference could be modulated by emotional messages contained in the description (i.e., frame) of options. The behavioral results have showed the classic framing effect. In addition, individual level of trait anxiety was positively correlated with the framing effect size. However, trait anxiety was not correlated with risk-avoidance ratio in any condition. Finally, the relationship between anxiety and the framing effect remained significant after the level of depression was also taken into account. The theoretical significance and the major limitations of this study are ...
β-amyloid (Aβ) plaques and tau-related neurodegeneration are pathologic hallmarks of Alzheimer's ... more β-amyloid (Aβ) plaques and tau-related neurodegeneration are pathologic hallmarks of Alzheimer's disease (AD). The utility of AD biomarkers, including those measured in cerebrospinal fluid (CSF), in predicting future AD risk and cognitive decline is still being refined. Here, we explored potential relationships between functional connectivity (FC) patterns within the default-mode network (DMN), age, CSF biomarkers (Aβ42 and pTau181), and cognitive status in older adults. Multiple measures of FC were explored, including a novel time series-based measure [total interdependence (TI)]. In our sample of 27 cognitively normal older adults, no significant associations were found between levels of Aβ42 or pTau181 and cognitive scores or regional brain volumes. However, we observed several novel relationships between these biomarkers and measures of FC in DMN during both resting-state and a short-term memory task. First, increased connectivity between bilateral anterior middle temporal gyri was associated with higher levels of CSF Aβ42 and Aβ42/pTau181 ratio (reflecting lower AD risk) during both rest and task. Second, increased bilateral parietal connectivity during the short-term memory task, but not during rest, was associated with higher levels of CSF pTau181 (reflecting higher AD risk). Third, increased connectivity between left middle temporal and left parietal cortices during the active task was associated with decreased global cognitive status but not CSF biomarkers. Lastly, we found that our new TI method was more sensitive to the CSF Aβ42-connectivity relationship whereas the traditional cross-correlation method was more sensitive to levels of CSF pTau181 and cognitive status. With further refinement, resting-state connectivity and task-driven connectivity measures hold promise as non-invasive neuroimaging markers of Aβ and pTau burden in cognitively normal older adults.
Individuals with genotypes that code for reduced dopaminergic brain activity often exhibit a pred... more Individuals with genotypes that code for reduced dopaminergic brain activity often exhibit a predisposition towards aggression. However, it remains largely unknown how dopaminergic genotypes may increase aggression. Lower-functioning dopamine systems motivate individuals to seek reward from external sources such as illicit drugs and other risky experiences. Based on emerging evidence that aggression is a rewarding experience, we predicted that the effect of lower-functioning dopaminergic functioning on aggression would be mediated by tendencies to seek the environment for rewards. Caucasian female and male undergraduates (N = 277) were genotyped for five polymorphisms of the Dopamine D2 Receptor (DRD2) gene, reported their previous history of aggression, and their dispositional reward-seeking. Lower-functioning DRD2 profiles were associated with greater sensation-seeking, which then predicted greater aggression. Our findings suggest that lower-functioning dopaminergic activity puts ...
Background: Early prognosis of high-risk older adults for amnestic mild cognitive impairment (aMC... more Background: Early prognosis of high-risk older adults for amnestic mild cognitive impairment (aMCI), using noninvasive and sensitive neuromarkers, is key for early prevention of Alzheimer’s disease. We have developed individualized measures in electrophysiological brain signals during working memory that distinguish patients with aMCI from age-matched cognitively intact older individuals. Objective: Here we test longitudinally the prognosis of the baseline neuromarkers for aMCI risk. We hypothesized that the older individuals diagnosed with incident aMCI already have aMCI-like brain signatures years before diagnosis. Methods: Electroencephalogram (EEG) and memory performance were recorded during a working memory task at baseline. The individualized baseline neuromarkers, annual cognitive status, and longitudinal changes in memory recall scores up to 10 years were analyzed. Results: Seven of the 19 cognitively normal older adults were diagnosed with incident aMCI for a median 5.2 yea...
The perception of a stimulus can be influenced by previous perceptual experience, a phenomenon kn... more The perception of a stimulus can be influenced by previous perceptual experience, a phenomenon known as perceptual priming. However, there has been limited investigation on perceptual priming of shape perception of three-dimensional object structures defined by moving dots. Here we examined the perceptual priming of a 3D object shape defined purely by motion-in-depth cues (i.e., Shape-From-Motion, SFM) using a classic prime-target paradigm. The results from the first two experiments revealed a significant increase in accuracy when a "cloudy" SFM stimulus (whose object structure was difficult to recognize due to the presence of strong noise) was preceded by an unambiguous SFM that clearly defined the same transparent 3D shape. In contrast, results from Experiment 3 revealed no change in accuracy when a "cloudy" SFM stimulus was preceded by a static shape or a semantic word that defined the same object shape. Instead, there was a significant decrease in accuracy when preceded by a static shape or a semantic word that defined a different object shape. These results suggested that the perception of a noisy SFM stimulus can be facilitated by a preceding unambiguous SFM stimulus-but not a static image or a semantic stimulus-that defined the same shape. The potential neural and computational mechanisms underlying the difference in priming are discussed.
Speed of visual word recognition is an important variable affecting linguistic competence. Althou... more Speed of visual word recognition is an important variable affecting linguistic competence. Although speed of visual word recognition varies widely between individuals, the neural basis of reaction time (RT) differences is poorly understood. Recently, a magnetic resonance technique called diffusion tensor imaging (DTI) has been shown to provide information about white matter (WM) microstructure in vivo. Here, we used DTI to explore whether visual word recognition RT correlates with regional fractional anisotropy (FA) values in the WM of healthy young adults. Participants completed a speeded lexical decision task that involved visual input, linguistic processes, and a motor response output. Results indicated that lexical decision RT was correlated negatively with FA in WM of inferior parietal and frontal language regions rather than in WM of visual or motor regions. Voxels within the inferior parietal and frontal correlation clusters were composed primarily of DTI-based tracts oriented in the anterior-posterior orientation at or near the superior longitudinal fasciculus (SLF) and likely including other smaller association fibers. These results provide new microstructural evidence demonstrating that speed of lexical decision is associated with the degree to which portions of frontal and parietal WM are directionally oriented.
Background / Purpose: We investigated whether the slower reaction times observed in older adults ... more Background / Purpose: We investigated whether the slower reaction times observed in older adults in cognitive tasks is more than slowed neural responses. We hypothesize that the general response slowing is contributed by not just slowed processing speed, but also involves the early engagement of additional cortices, and hence a longer processing time in older adults' brains compared to those in the young. Main conclusion: Using time-sensitive and localized event-related potential (ERP) measures, we provide new evidence that generally slower processing time during a working memory task in older adults is partially due to the fact that older adults engaged the frontal cortex several hundred milliseconds earlier compared to young adults. The “detour” to frontal lobe contributes to age-related differences in reaction times for performance-matched working memory retrieval.
The neural correlates of the motion priming were examined in normal young subjects using event-re... more The neural correlates of the motion priming were examined in normal young subjects using event-related brain potentials (ERPs) and functional magnetic resonance imaging (fMRI). Visual motion perception can be unconsciously biased in favor of a particular direction by a preceding motion in that direction. Motion priming first involved an enhancement of ERP amplitude about 100 ms following the onset of motion. The amplitudes of ERP components after 350 ms were also increased. The fMRI results suggest that the early-latency effect reflects modulation of neural responses in extrastriate cortex. Higher-level visual processing areas, including cortical regions MT/MST and the intraparietal cortices were also activated. The findings provide direct evidence that unconscious priming of motion perception is the result of interaction of direction-selective neural responses to motion stimuli. The results cannot be accounted for by refractoriness of neural responses, but instead support a theory of motion priming based on motion opponency, as proposed in computational models.
Normal aging is associated with greater decline in associative memory relative to item memory due... more Normal aging is associated with greater decline in associative memory relative to item memory due to impaired recollection. Familiarity may also contribute to associative recognition when stimuli are perceived as a 'unitized' representation. Given that familiarity is relatively preserved in older adults, we explored whether age-related associative memory deficits could be attenuated when associations were unitized (i.e., compounds) compared with those non-unitized (i.e., unrelated word pairs). Young and older adults performed an associative recognition task while electroencephalogram (EEG) was recorded. Behavioral results showed that age differences were smaller for recognition of compounds than for unrelated word pairs. ERP results indicated that only compounds evoked an early frontal old/new effect in older adults. Moreover, the early frontal old/new effect was positively correlated with associative discrimination accuracy. These findings suggest that reduced age-related a...
Proceedings of the 2014 Biomedical Sciences and Engineering Conference, 2014
ABSTRACT Mild cognitive impairment (MCI) is a neurological condition that is often the early stag... more ABSTRACT Mild cognitive impairment (MCI) is a neurological condition that is often the early stage of Alzheimer's disease (AD). This pilot study explores event-related multiscale entropy (MSE) measures as features for effectively discriminating between normal aging, MCI, and AD participants. Thirty two-channel scalp EEG records recorded during a working memory task from 43 age-matched participants (mean age 75.7 years)-17 normal controls (NC), 16 MCI, and 10 early ADare examined. Multiscale entropy curves are computed for responses during the working memory task. Support vector machine models are constructed to perform binary discriminations among the three groups. Leave-one-out cross-validation accuracies of 87.9% (p-value <1.322E-4) for MCI vs. NC, 88.9% (p-value <2.886E-5) for AD vs. NC, and 92.3% (p-value <4.910E-6) for MCI vs. AD are achieved. Results demonstrate links between event-related multiscale entropy dynamics of EEG and short-term memory deficits.
2013 Biomedical Sciences and Engineering Conference (BSEC), 2013
ABSTRACT Mild cognitive impairment (MCI) is a neurological disease which is often comorbid with e... more ABSTRACT Mild cognitive impairment (MCI) is a neurological disease which is often comorbid with early stages of Alzheimer's disease (AD). This study explores the potential for detecting changes in neurological functional organization which may be indicative of MCI and early AD using neural network models for scalp EEG signal reconstruction. Resting 32-channel EEG records from 48 age-matched participants (mean age 75.7 years)-15 normal controls (NC), 16 MCI, and 17 early-stage AD-are examined. Neural network models are trained to reconstruct artificially “deleted” samples of EEG using subsets of records from NC participants. Models are applied to EEG records and quality scores are assigned to reconstructions of individual channels. Principal components of regional average reconstruction quality scores are used in a support vector machine model to discriminate between groups. Analyses demonstrate accuracies of 90.3% for MCI vs. NC (p-value
White matter (WM) microstructural declines have been demonstrated in Alzheimer's disease and ... more White matter (WM) microstructural declines have been demonstrated in Alzheimer's disease and amnestic mild cognitive impairment (aMCI). However, the pattern of WM microstructural changes in aMCI after controlling for WM atrophy is unknown. Here, we address this issue through joint consideration of aMCI alterations in fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity, as well as macrostructural volume in WM and gray matter compartments. Participants were 18 individuals with aMCI and 24 healthy seniors. Voxelwise analyses of diffusion tensor imaging data was carried out using tract-based spatial statistics (TBSS) and voxelwise analyses of high-resolution structural data was conducted using voxel based morphometry. After controlling for WM atrophy, the main pattern of TBSS findings indicated reduced fractional anisotropy with only small alterations in mean diffusivity/radial diffusivity/axial diffusivity. These WM microstructural declines bordered a...
Neurological abnormalities have been reported in people with amnestic mild cognitive impairment (... more Neurological abnormalities have been reported in people with amnestic mild cognitive impairment (aMCI). The current study aimed to examine the prevalence of neurological soft signs (NSS) in this clinical group and to examine the relationship of NSS to other neuropsychological performances. Twenty-nine people with aMCI and 28 cognitively healthy elderly people were recruited for the present study. The NSS subscales (motor coordination, sensory integration, and disinhibition) of the Cambridge Neurological Inventory and a set of neuropsychological tests were administered to all the participants. People with aMCI exhibited significantly more motor coordination signs, disinhibition signs, and total NSS than normal controls. Correlation analysis showed that the motor coordination subscale score and total score of NSS were significantly inversely correlated with the combined Z-score of neuropsychological tests in aMCI group. These preliminary findings suggested that people with aMCI demons...
Both visual object priming and motion priming have been reported independently, but the interacti... more Both visual object priming and motion priming have been reported independently, but the interactions between the two are still largely unexplored. Here we investigated this question using a novel type of SFM stimuli, 3-D helixes, and found that the motion direction perception of an ambiguous helix can be biased by the motion direction of a preceding SFM stimulus - a classic motion priming effect. However, the effectiveness of motion priming depends on object priming: a neutral object priming produced a weak motion priming, a congruent object priming led to a strong motion priming, and critically, an incongruent object priming abolished and overpowered the motion priming. In contrast, object priming alone (in the absence of motion overlap) had little effects biasing motion perception. Taken together, these results suggest that there exists an integrated neural representation of motion and structure of 3-D SFM stimuli, and motion priming of 3-D SFM stimuli might happen at an intermedi...
International journal of psychophysiology : official journal of the International Organization of Psychophysiology, Jan 10, 2015
Familiarity and recollection are two independent cognitive processes involved in recognition memo... more Familiarity and recollection are two independent cognitive processes involved in recognition memory. It is traditionally believed that both familiarity and recollection can support item recognition, whereas only recollection can support associative recognition. Here, using a standard associative recognition task, we examined whether associative retrieval of unitized associations involved differential patterns of familiarity and recollection processes relative to non-unitized associations. The extent of engagement of familiarity and recollection processes during associative retrieval was estimated by using event-related potentials (ERPs). Twenty participants studied compound words and unrelated word pairs during encoding. Subsequently, they were asked to decide whether a presented word pair was intact, rearranged, or a new pair while electroencephalogram (EEG) was recorded. ERP results showed that compound words evoked a significant early frontal old/new effect (associated with famil...
How do visual luminance, shape, motion, and depth bind together in the brain to represent the coh... more How do visual luminance, shape, motion, and depth bind together in the brain to represent the coherent percept of a 3-D object within hundreds of milliseconds (msec)? We provide evidence from simultaneous magnetoencephalographic (MEG) and electroencephalographic (EEG) data that perception of 3-D objects defined by luminance or motion elicits sequential activity in human visual cortices within 500 msec. Following activation of the primary visual cortex around 100 msec, 3-D objects elicited sequential activity with only little overlap (dynamic 3-D shapes: MT-LO-Temp; stationary 3-D shapes: LO-Temp). A delay of 80 msec, both in MEG/EEG responses and in reaction times (RTs), was found when additional motion information was processed. We also found significant positive correlations between RT, and MEG and EEG responses in the right temporal location. After about 400 msec, long-lasting activity was observed in the parietal cortex and concurrently in previously activated regions. Novel tim...
Cortex; a journal devoted to the study of the nervous system and behavior, 2018
The default mode network (DMN) comprises defined brain regions contributing to internally-directe... more The default mode network (DMN) comprises defined brain regions contributing to internally-directed thought processes. Reductions in task-induced deactivation in the DMN have been associated with increasing age and poorer executive task performance, but factors underlying these functional changes remain unclear. We investigated contributions of white matter (WM) microstructure, WM hyperintensities (WMH) and Alzheimer's pathology to age-related alterations in DMN function. Thirty-five cognitively normal older adults and 29 younger adults underwent working memory task fMRI and diffusion tensor imaging. In the older adults, we measured cerebrospinal fluid tau and Aβ (markers of AD pathology), and WMH on FLAIR imaging (marker of cerebrovascular disease). We identified a set of regions showing DMN deactivation and a set of inter-connecting WM tracts (DMN-WM) common to both age groups. There were negative associations between DMN deactivation and task performance in older adults, consi...
Forms of implicit memory, including repetition effects, are preserved relative to explicit memory... more Forms of implicit memory, including repetition effects, are preserved relative to explicit memory in clinical Alzheimer's disease. Consequently, cognitive interventions for persons with Alzheimer's disease have been developed that leverage this fact. However, despite the clinical robustness of behavioral repetition effects, altered neural mechanisms of repetition effects are studied as biomarkers of both clinical Alzheimer's disease and pre-morbid Alzheimer's changes in the brain. We hypothesized that the clinical preservation of behavioral repetition effects results in part from concurrent operation of discrete memory systems. We developed two experiments that included probes of emotional repetition effects differing in that one included an embedded working memory task. We found that neural repetition effects manifested in patients with amnestic mild cognitive impairment, the earliest form of clinical Alzheimer's disease, during emotional working memory tasks, b...
Neurofeedback (NF) is a form of biofeedback that uses real-time (RT) modulation of brain activity... more Neurofeedback (NF) is a form of biofeedback that uses real-time (RT) modulation of brain activity to enhance brain function and behavioral performance. Recent advances in Brain-Computer Interfaces (BCI) and cognitive training (CT) have provided new tools and evidence that NF improves cognitive functions, such as attention and working memory (WM), beyond what is provided by traditional CT. More published studies have demonstrated the efficacy of NF, particularly for treating attention deficit hyperactivity disorder (ADHD) in children. In contrast, there have been fewer studies done in older adults with or without cognitive impairment, with some notable exceptions. The focus of this review is to summarize current success in RT NF training of older brains aiming to match those of younger brains during attention/WM tasks. We also outline potential future advances in RT brainwave-based NF for improving attention training in older populations. The rapid growth in wireless recording of bra...
According to previous literature, trait anxiety is related to the tendency to choose safety optio... more According to previous literature, trait anxiety is related to the tendency to choose safety options during risk decision-making, that is, risk avoidance. In our opinion, anxious people's risk preference might actually reflect their hypersensitivity to emotional information. To examine this hypothesis, a decision-making task that could elicit the framing effect was employed. The framing effect indicates that risk preference could be modulated by emotional messages contained in the description (i.e., frame) of options. The behavioral results have showed the classic framing effect. In addition, individual level of trait anxiety was positively correlated with the framing effect size. However, trait anxiety was not correlated with risk-avoidance ratio in any condition. Finally, the relationship between anxiety and the framing effect remained significant after the level of depression was also taken into account. The theoretical significance and the major limitations of this study are ...
β-amyloid (Aβ) plaques and tau-related neurodegeneration are pathologic hallmarks of Alzheimer's ... more β-amyloid (Aβ) plaques and tau-related neurodegeneration are pathologic hallmarks of Alzheimer's disease (AD). The utility of AD biomarkers, including those measured in cerebrospinal fluid (CSF), in predicting future AD risk and cognitive decline is still being refined. Here, we explored potential relationships between functional connectivity (FC) patterns within the default-mode network (DMN), age, CSF biomarkers (Aβ42 and pTau181), and cognitive status in older adults. Multiple measures of FC were explored, including a novel time series-based measure [total interdependence (TI)]. In our sample of 27 cognitively normal older adults, no significant associations were found between levels of Aβ42 or pTau181 and cognitive scores or regional brain volumes. However, we observed several novel relationships between these biomarkers and measures of FC in DMN during both resting-state and a short-term memory task. First, increased connectivity between bilateral anterior middle temporal gyri was associated with higher levels of CSF Aβ42 and Aβ42/pTau181 ratio (reflecting lower AD risk) during both rest and task. Second, increased bilateral parietal connectivity during the short-term memory task, but not during rest, was associated with higher levels of CSF pTau181 (reflecting higher AD risk). Third, increased connectivity between left middle temporal and left parietal cortices during the active task was associated with decreased global cognitive status but not CSF biomarkers. Lastly, we found that our new TI method was more sensitive to the CSF Aβ42-connectivity relationship whereas the traditional cross-correlation method was more sensitive to levels of CSF pTau181 and cognitive status. With further refinement, resting-state connectivity and task-driven connectivity measures hold promise as non-invasive neuroimaging markers of Aβ and pTau burden in cognitively normal older adults.
Individuals with genotypes that code for reduced dopaminergic brain activity often exhibit a pred... more Individuals with genotypes that code for reduced dopaminergic brain activity often exhibit a predisposition towards aggression. However, it remains largely unknown how dopaminergic genotypes may increase aggression. Lower-functioning dopamine systems motivate individuals to seek reward from external sources such as illicit drugs and other risky experiences. Based on emerging evidence that aggression is a rewarding experience, we predicted that the effect of lower-functioning dopaminergic functioning on aggression would be mediated by tendencies to seek the environment for rewards. Caucasian female and male undergraduates (N = 277) were genotyped for five polymorphisms of the Dopamine D2 Receptor (DRD2) gene, reported their previous history of aggression, and their dispositional reward-seeking. Lower-functioning DRD2 profiles were associated with greater sensation-seeking, which then predicted greater aggression. Our findings suggest that lower-functioning dopaminergic activity puts ...
Background: Early prognosis of high-risk older adults for amnestic mild cognitive impairment (aMC... more Background: Early prognosis of high-risk older adults for amnestic mild cognitive impairment (aMCI), using noninvasive and sensitive neuromarkers, is key for early prevention of Alzheimer’s disease. We have developed individualized measures in electrophysiological brain signals during working memory that distinguish patients with aMCI from age-matched cognitively intact older individuals. Objective: Here we test longitudinally the prognosis of the baseline neuromarkers for aMCI risk. We hypothesized that the older individuals diagnosed with incident aMCI already have aMCI-like brain signatures years before diagnosis. Methods: Electroencephalogram (EEG) and memory performance were recorded during a working memory task at baseline. The individualized baseline neuromarkers, annual cognitive status, and longitudinal changes in memory recall scores up to 10 years were analyzed. Results: Seven of the 19 cognitively normal older adults were diagnosed with incident aMCI for a median 5.2 yea...
The perception of a stimulus can be influenced by previous perceptual experience, a phenomenon kn... more The perception of a stimulus can be influenced by previous perceptual experience, a phenomenon known as perceptual priming. However, there has been limited investigation on perceptual priming of shape perception of three-dimensional object structures defined by moving dots. Here we examined the perceptual priming of a 3D object shape defined purely by motion-in-depth cues (i.e., Shape-From-Motion, SFM) using a classic prime-target paradigm. The results from the first two experiments revealed a significant increase in accuracy when a "cloudy" SFM stimulus (whose object structure was difficult to recognize due to the presence of strong noise) was preceded by an unambiguous SFM that clearly defined the same transparent 3D shape. In contrast, results from Experiment 3 revealed no change in accuracy when a "cloudy" SFM stimulus was preceded by a static shape or a semantic word that defined the same object shape. Instead, there was a significant decrease in accuracy when preceded by a static shape or a semantic word that defined a different object shape. These results suggested that the perception of a noisy SFM stimulus can be facilitated by a preceding unambiguous SFM stimulus-but not a static image or a semantic stimulus-that defined the same shape. The potential neural and computational mechanisms underlying the difference in priming are discussed.
Speed of visual word recognition is an important variable affecting linguistic competence. Althou... more Speed of visual word recognition is an important variable affecting linguistic competence. Although speed of visual word recognition varies widely between individuals, the neural basis of reaction time (RT) differences is poorly understood. Recently, a magnetic resonance technique called diffusion tensor imaging (DTI) has been shown to provide information about white matter (WM) microstructure in vivo. Here, we used DTI to explore whether visual word recognition RT correlates with regional fractional anisotropy (FA) values in the WM of healthy young adults. Participants completed a speeded lexical decision task that involved visual input, linguistic processes, and a motor response output. Results indicated that lexical decision RT was correlated negatively with FA in WM of inferior parietal and frontal language regions rather than in WM of visual or motor regions. Voxels within the inferior parietal and frontal correlation clusters were composed primarily of DTI-based tracts oriented in the anterior-posterior orientation at or near the superior longitudinal fasciculus (SLF) and likely including other smaller association fibers. These results provide new microstructural evidence demonstrating that speed of lexical decision is associated with the degree to which portions of frontal and parietal WM are directionally oriented.
Background / Purpose: We investigated whether the slower reaction times observed in older adults ... more Background / Purpose: We investigated whether the slower reaction times observed in older adults in cognitive tasks is more than slowed neural responses. We hypothesize that the general response slowing is contributed by not just slowed processing speed, but also involves the early engagement of additional cortices, and hence a longer processing time in older adults' brains compared to those in the young. Main conclusion: Using time-sensitive and localized event-related potential (ERP) measures, we provide new evidence that generally slower processing time during a working memory task in older adults is partially due to the fact that older adults engaged the frontal cortex several hundred milliseconds earlier compared to young adults. The “detour” to frontal lobe contributes to age-related differences in reaction times for performance-matched working memory retrieval.
The neural correlates of the motion priming were examined in normal young subjects using event-re... more The neural correlates of the motion priming were examined in normal young subjects using event-related brain potentials (ERPs) and functional magnetic resonance imaging (fMRI). Visual motion perception can be unconsciously biased in favor of a particular direction by a preceding motion in that direction. Motion priming first involved an enhancement of ERP amplitude about 100 ms following the onset of motion. The amplitudes of ERP components after 350 ms were also increased. The fMRI results suggest that the early-latency effect reflects modulation of neural responses in extrastriate cortex. Higher-level visual processing areas, including cortical regions MT/MST and the intraparietal cortices were also activated. The findings provide direct evidence that unconscious priming of motion perception is the result of interaction of direction-selective neural responses to motion stimuli. The results cannot be accounted for by refractoriness of neural responses, but instead support a theory of motion priming based on motion opponency, as proposed in computational models.
Normal aging is associated with greater decline in associative memory relative to item memory due... more Normal aging is associated with greater decline in associative memory relative to item memory due to impaired recollection. Familiarity may also contribute to associative recognition when stimuli are perceived as a 'unitized' representation. Given that familiarity is relatively preserved in older adults, we explored whether age-related associative memory deficits could be attenuated when associations were unitized (i.e., compounds) compared with those non-unitized (i.e., unrelated word pairs). Young and older adults performed an associative recognition task while electroencephalogram (EEG) was recorded. Behavioral results showed that age differences were smaller for recognition of compounds than for unrelated word pairs. ERP results indicated that only compounds evoked an early frontal old/new effect in older adults. Moreover, the early frontal old/new effect was positively correlated with associative discrimination accuracy. These findings suggest that reduced age-related a...
Proceedings of the 2014 Biomedical Sciences and Engineering Conference, 2014
ABSTRACT Mild cognitive impairment (MCI) is a neurological condition that is often the early stag... more ABSTRACT Mild cognitive impairment (MCI) is a neurological condition that is often the early stage of Alzheimer's disease (AD). This pilot study explores event-related multiscale entropy (MSE) measures as features for effectively discriminating between normal aging, MCI, and AD participants. Thirty two-channel scalp EEG records recorded during a working memory task from 43 age-matched participants (mean age 75.7 years)-17 normal controls (NC), 16 MCI, and 10 early ADare examined. Multiscale entropy curves are computed for responses during the working memory task. Support vector machine models are constructed to perform binary discriminations among the three groups. Leave-one-out cross-validation accuracies of 87.9% (p-value <1.322E-4) for MCI vs. NC, 88.9% (p-value <2.886E-5) for AD vs. NC, and 92.3% (p-value <4.910E-6) for MCI vs. AD are achieved. Results demonstrate links between event-related multiscale entropy dynamics of EEG and short-term memory deficits.
2013 Biomedical Sciences and Engineering Conference (BSEC), 2013
ABSTRACT Mild cognitive impairment (MCI) is a neurological disease which is often comorbid with e... more ABSTRACT Mild cognitive impairment (MCI) is a neurological disease which is often comorbid with early stages of Alzheimer's disease (AD). This study explores the potential for detecting changes in neurological functional organization which may be indicative of MCI and early AD using neural network models for scalp EEG signal reconstruction. Resting 32-channel EEG records from 48 age-matched participants (mean age 75.7 years)-15 normal controls (NC), 16 MCI, and 17 early-stage AD-are examined. Neural network models are trained to reconstruct artificially “deleted” samples of EEG using subsets of records from NC participants. Models are applied to EEG records and quality scores are assigned to reconstructions of individual channels. Principal components of regional average reconstruction quality scores are used in a support vector machine model to discriminate between groups. Analyses demonstrate accuracies of 90.3% for MCI vs. NC (p-value
White matter (WM) microstructural declines have been demonstrated in Alzheimer's disease and ... more White matter (WM) microstructural declines have been demonstrated in Alzheimer's disease and amnestic mild cognitive impairment (aMCI). However, the pattern of WM microstructural changes in aMCI after controlling for WM atrophy is unknown. Here, we address this issue through joint consideration of aMCI alterations in fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity, as well as macrostructural volume in WM and gray matter compartments. Participants were 18 individuals with aMCI and 24 healthy seniors. Voxelwise analyses of diffusion tensor imaging data was carried out using tract-based spatial statistics (TBSS) and voxelwise analyses of high-resolution structural data was conducted using voxel based morphometry. After controlling for WM atrophy, the main pattern of TBSS findings indicated reduced fractional anisotropy with only small alterations in mean diffusivity/radial diffusivity/axial diffusivity. These WM microstructural declines bordered a...
Neurological abnormalities have been reported in people with amnestic mild cognitive impairment (... more Neurological abnormalities have been reported in people with amnestic mild cognitive impairment (aMCI). The current study aimed to examine the prevalence of neurological soft signs (NSS) in this clinical group and to examine the relationship of NSS to other neuropsychological performances. Twenty-nine people with aMCI and 28 cognitively healthy elderly people were recruited for the present study. The NSS subscales (motor coordination, sensory integration, and disinhibition) of the Cambridge Neurological Inventory and a set of neuropsychological tests were administered to all the participants. People with aMCI exhibited significantly more motor coordination signs, disinhibition signs, and total NSS than normal controls. Correlation analysis showed that the motor coordination subscale score and total score of NSS were significantly inversely correlated with the combined Z-score of neuropsychological tests in aMCI group. These preliminary findings suggested that people with aMCI demons...
Both visual object priming and motion priming have been reported independently, but the interacti... more Both visual object priming and motion priming have been reported independently, but the interactions between the two are still largely unexplored. Here we investigated this question using a novel type of SFM stimuli, 3-D helixes, and found that the motion direction perception of an ambiguous helix can be biased by the motion direction of a preceding SFM stimulus - a classic motion priming effect. However, the effectiveness of motion priming depends on object priming: a neutral object priming produced a weak motion priming, a congruent object priming led to a strong motion priming, and critically, an incongruent object priming abolished and overpowered the motion priming. In contrast, object priming alone (in the absence of motion overlap) had little effects biasing motion perception. Taken together, these results suggest that there exists an integrated neural representation of motion and structure of 3-D SFM stimuli, and motion priming of 3-D SFM stimuli might happen at an intermedi...
International journal of psychophysiology : official journal of the International Organization of Psychophysiology, Jan 10, 2015
Familiarity and recollection are two independent cognitive processes involved in recognition memo... more Familiarity and recollection are two independent cognitive processes involved in recognition memory. It is traditionally believed that both familiarity and recollection can support item recognition, whereas only recollection can support associative recognition. Here, using a standard associative recognition task, we examined whether associative retrieval of unitized associations involved differential patterns of familiarity and recollection processes relative to non-unitized associations. The extent of engagement of familiarity and recollection processes during associative retrieval was estimated by using event-related potentials (ERPs). Twenty participants studied compound words and unrelated word pairs during encoding. Subsequently, they were asked to decide whether a presented word pair was intact, rearranged, or a new pair while electroencephalogram (EEG) was recorded. ERP results showed that compound words evoked a significant early frontal old/new effect (associated with famil...
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Papers by Yang Jiang