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A Multivariate Method To Determine The Dimensionality Of Neural Representation From Population Activity., Jörn Diedrichsen, Tobias Wiestler, Naveed Ejaz
A Multivariate Method To Determine The Dimensionality Of Neural Representation From Population Activity., Jörn Diedrichsen, Tobias Wiestler, Naveed Ejaz
Brain and Mind Institute Researchers' Publications
How do populations of neurons represent a variable of interest? The notion of feature spaces is a useful concept to approach this question: According to this model, the activation patterns across a neuronal population are composed of different pattern components. The strength of each of these components varies with one latent feature, which together are the dimensions along which the population represents the variable. Here we propose a new method to determine the number of feature dimensions that best describes the activation patterns. The method is based on Gaussian linear classifiers that use only the first d most important pattern …
Erps Reveal The Temporal Dynamics Of Auditory Word Recognition In Specific Language Impairment., Jeffrey G Malins, Amy S Desroches, Erin K Robertson, Randy Lynn Newman, Lisa M D Archibald, Marc F Joanisse
Erps Reveal The Temporal Dynamics Of Auditory Word Recognition In Specific Language Impairment., Jeffrey G Malins, Amy S Desroches, Erin K Robertson, Randy Lynn Newman, Lisa M D Archibald, Marc F Joanisse
Brain and Mind Institute Researchers' Publications
We used event-related potentials (ERPs) to compare auditory word recognition in children with specific language impairment (SLI group; N=14) to a group of typically developing children (TD group; N=14). Subjects were presented with pictures of items and heard auditory words that either matched or mismatched the pictures. Mismatches overlapped expected words in word-onset (cohort mismatches; see: DOLL, hear: dog), rhyme (CONE -bone), or were unrelated (SHELL -mug). In match trials, the SLI group showed a different pattern of N100 responses to auditory stimuli compared to the TD group, indicative of early auditory processing differences in SLI. However, the phonological mapping …
Dynamic And Opposing Adjustment Of Movement Cancellation And Generation In An Oculomotor Countermanding Task., Brian D Corneil, Joshua C Cheng, Samanthi C Goonetilleke
Dynamic And Opposing Adjustment Of Movement Cancellation And Generation In An Oculomotor Countermanding Task., Brian D Corneil, Joshua C Cheng, Samanthi C Goonetilleke
Brain and Mind Institute Researchers' Publications
Adaptive adjustments of strategies help optimize behavior in a dynamic and uncertain world. Previous studies in the countermanding (or stop-signal) paradigm have detailed how reaction times (RTs) change with trial sequence, demonstrating adaptive control of movement generation. Comparatively little is known about the adaptive control of movement cancellation in the countermanding task, mainly because movement cancellation implies the absence of an outcome and estimates of movement cancellation require hundreds of trials. Here, we exploit a within-trial proxy of movement cancellation based on recordings of neck muscle activity while human subjects attempted to cancel large eye-head gaze shifts. On a subset …
Two Distinct Ipsilateral Cortical Representations For Individuated Finger Movements., Jörn Diedrichsen, Tobias Wiestler, John W Krakauer
Two Distinct Ipsilateral Cortical Representations For Individuated Finger Movements., Jörn Diedrichsen, Tobias Wiestler, John W Krakauer
Brain and Mind Institute Researchers' Publications
Movements of the upper limb are controlled mostly through the contralateral hemisphere. Although overall activity changes in the ipsilateral motor cortex have been reported, their functional significance remains unclear. Using human functional imaging, we analyzed neural finger representations by studying differences in fine-grained activation patterns for single isometric finger presses. We demonstrate that cortical motor areas encode ipsilateral movements in 2 fundamentally different ways. During unimanual ipsilateral finger presses, primary sensory and motor cortices show, underneath global suppression, finger-specific activity patterns that are nearly identical to those elicited by contralateral mirror-symmetric action. This component vanishes when both motor cortices are …
Prefrontal Neurons Of Opposite Spatial Preference Display Distinct Target Selection Dynamics., Therese Lennert, Julio C Martinez-Trujillo
Prefrontal Neurons Of Opposite Spatial Preference Display Distinct Target Selection Dynamics., Therese Lennert, Julio C Martinez-Trujillo
Brain and Mind Institute Researchers' Publications
Neurons in the primate dorsolateral prefrontal cortex (dlPFC) of one hemisphere are selective for the location of attended targets in both visual hemifields. Whether dlPFC neurons with selectivity for opposite hemifields directly compete with each other for target selection or instead play distinct roles during the allocation of attention remains unclear. We explored this issue by recording neuronal responses in the right dlPFC of two macaques while they allocated attention to a target in one hemifield and ignored a distracter on the opposite side. Forty-nine percent of the recorded neurons were target location selective. Neurons selective for contralateral targets (58%) …
Decoding The Neural Mechanisms Of Human Tool Use., Jason P Gallivan, D Adam Mclean, Kenneth F Valyear, Jody C Culham
Decoding The Neural Mechanisms Of Human Tool Use., Jason P Gallivan, D Adam Mclean, Kenneth F Valyear, Jody C Culham
Brain and Mind Institute Researchers' Publications
Sophisticated tool use is a defining characteristic of the primate species but how is it supported by the brain, particularly the human brain? Here we show, using functional MRI and pattern classification methods, that tool use is subserved by multiple distributed action-centred neural representations that are both shared with and distinct from those of the hand. In areas of frontoparietal cortex we found a common representation for planned hand- and tool-related actions. In contrast, in parietal and occipitotemporal regions implicated in hand actions and body perception we found that coding remained selectively linked to upcoming actions of the hand whereas …
The Human Brain Processes Syntax In The Absence Of Conscious Awareness., Laura Batterink, Helen J Neville
The Human Brain Processes Syntax In The Absence Of Conscious Awareness., Laura Batterink, Helen J Neville
Brain and Mind Institute Researchers' Publications
Syntax is the core computational component of language. A longstanding idea about syntactic processing is that it is generally not available to conscious access, operating autonomously and automatically. However, there is little direct neurocognitive evidence on this issue. By measuring event-related potentials while human observers performed a novel cross-modal distraction task, we demonstrated that syntactic violations that were not consciously detected nonetheless produced a characteristic early neural response pattern, and also significantly delayed reaction times to a concurrent task. This early neural response was distinct from later neural activity that was observed only to syntactic violations that were consciously detected. …
Acute Alcohol Consumption Impairs Controlled But Not Automatic Processes In A Psychophysical Pointing Paradigm., Kevin Johnston, Brian Timney, Melvyn A Goodale
Acute Alcohol Consumption Impairs Controlled But Not Automatic Processes In A Psychophysical Pointing Paradigm., Kevin Johnston, Brian Timney, Melvyn A Goodale
Brain and Mind Institute Researchers' Publications
Numerous studies have investigated the effects of alcohol consumption on controlled and automatic cognitive processes. Such studies have shown that alcohol impairs performance on tasks requiring conscious, intentional control, while leaving automatic performance relatively intact. Here, we sought to extend these findings to aspects of visuomotor control by investigating the effects of alcohol in a visuomotor pointing paradigm that allowed us to separate the influence of controlled and automatic processes. Six male participants were assigned to an experimental "correction" condition in which they were instructed to point at a visual target as quickly and accurately as possible. On a small …
Mice With Deficient Bk Channel Function Show Impaired Prepulse Inhibition And Spatial Learning, But Normal Working And Spatial Reference Memory., Marei Typlt, Magdalena Mirkowski, Erin Azzopardi, Lukas Ruettiger, Peter Ruth, Susanne Schmid
Mice With Deficient Bk Channel Function Show Impaired Prepulse Inhibition And Spatial Learning, But Normal Working And Spatial Reference Memory., Marei Typlt, Magdalena Mirkowski, Erin Azzopardi, Lukas Ruettiger, Peter Ruth, Susanne Schmid
Brain and Mind Institute Researchers' Publications
Genetic variations in the large-conductance, voltage- and calcium activated potassium channels (BK channels) have been recently implicated in mental retardation, autism and schizophrenia which all come along with severe cognitive impairments. In the present study we investigate the effects of functional BK channel deletion on cognition using a genetic mouse model with a knock-out of the gene for the pore forming α-subunit of the channel. We tested the F1 generation of a hybrid SV129/C57BL6 mouse line in which the slo1 gene was deleted in both parent strains. We first evaluated hearing and motor function to establish the suitability of this …