scholarly journals NEURAL ENCODING OF FELT AND IMAGINED TOUCH WITHIN HUMAN POSTERIOR PARIETAL CORTEX

2020 ◽  
Author(s):  
Srinivas Chivukula ◽  
Carey Zhang ◽  
Tyson Aflalo ◽  
Matiar Jafari ◽  
Kelsie Pejsa ◽  
...  
Keyword(s):  
Parietal Cortex ◽  
Semantic Processing ◽  
Posterior Parietal Cortex ◽  
Receptive Fields ◽  
Body Part ◽  
Neuronal Population ◽  
Movement Planning ◽  
Trial Participant ◽  
Motor Information ◽  
Posterior Parietal

ABSTRACTIn the human posterior parietal cortex (PPC), single units encode high-dimensional information with partially mixed representations that enable small populations of neurons to encode many variables relevant to movement planning, execution, cognition, and perception. Here we test whether a PPC neuronal population previously demonstrated to encode visual and motor information is similarly selective in the somatosensory domain. We recorded from 1423 neurons within the PPC of a human clinical trial participant during objective touch presentation and during tactile imagery. Neurons encoded experienced touch with bilateral receptive fields, organized by body part, and covered all tested regions. Tactile imagery evoked body part specific responses that shared a neural substrate with experienced touch. Our results are the first neuron level evidence of touch encoding in human PPC and its cognitive engagement during tactile imagery which may reflect semantic processing, sensory anticipation, and imagined touch.

scholarly journals Neural encoding of actual and imagined touch within human posterior parietal cortex

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Srinivas Chivukula ◽  
Carey Y Zhang ◽  
Tyson Aflalo ◽  
Matiar Jafari ◽  
Kelsie Pejsa ◽  
...  
Keyword(s):  
Parietal Cortex ◽  
Semantic Processing ◽  
Posterior Parietal Cortex ◽  
Receptive Fields ◽  
Body Part ◽  
Neuronal Population ◽  
Movement Planning ◽  
Trial Participant ◽  
Imagery Task ◽  
Posterior Parietal

In the human posterior parietal cortex (PPC), single units encode high-dimensional information with partially mixed representations that enable small populations of neurons to encode many variables relevant to movement planning, execution, cognition, and perception. Here, we test whether a PPC neuronal population previously demonstrated to encode visual and motor information is similarly engaged in the somatosensory domain. We recorded neurons within the PPC of a human clinical trial participant during actual touch presentation and during a tactile imagery task. Neurons encoded actual touch at short latency with bilateral receptive fields, organized by body part, and covered all tested regions. The tactile imagery task evoked body part-specific responses that shared a neural substrate with actual touch. Our results are the first neuron-level evidence of touch encoding in human PPC and its cognitive engagement during a tactile imagery task, which may reflect semantic processing, attention, sensory anticipation, or imagined touch.

scholarly journals Models of the Posterior Parietal Cortex Which Perform Multimodal Integration and Represent Space in Several Coordinate Frames

2000 ◽  
Vol 12 (4) ◽  
pp. 601-614 ◽  
Author(s):  
Jing Xing ◽  
Richard A. Andersen
Keyword(s):  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Receptive Fields ◽  
Activation Function ◽  
Head Position ◽  
Eye Position ◽  
Coordinate Transformations ◽  
Coordinate Frames ◽  
Single Output ◽  
Posterior Parietal

Many neurons in the posterior-parietal cortex (PPC) have saccadic responses to visual and auditory targets. The responses are modulated by eye position and head position. These findings suggest that PPC integrates multisensory inputs and may provide information about saccadic targets represented in different coordinate frames. In addition to an eye-centered output representation, PPC may also project to brain areas which contain head-centered and body-centered representations of the space. In this report, possible coordinate transformations in PPC were examined by comparing several sets of models of PPC, each having different representations in the output layer: (i) an eye-centered map only; (ii) a head-centered map only; (iii) an eye-centered map and a head-centered map; and (iv) an eye-centered map, a head-centered map, and a body-centered map. These output maps correctly encoded saccades to visual and auditory targets through training. The units in the hidden layers of the models exhibited the following properties: (1) The units had gain fields (GFs) for eye position, and also for head position if the model had a body-centered output representation; (2) As the result of the GF and the nonlinear activation function of the units, the hidden layers often employed “intermediate” coding, e.g., the hidden units coded targets partially in eye-centered coordinates and, partially, in head-centered coordinates; (3) Different types of coordinate transformations in these models were carried out by different relationships between the receptive fields (RFs) and the GFs of the hidden units; and (4) The properties of PPC neurons are in better accordance with the hidden units of the models that had multiple-output representations than the models that had only one single-output representation. In conclusion, the results show that the GF is an effective mechanism for performing coordinate transformations. The models also suggest that neurons with intermediate coding are to be expected in the process of coordinate transformations.

scholarly journals Single unit activity in marmoset posterior parietal cortex in a gap saccade task

2019 ◽  
Author(s):  
Liya Ma ◽  
Janahan Selvanayagam ◽  
Maryam Ghahremani ◽  
Lauren K. Hayrynen ◽  
Kevin D. Johnston ◽  
...  
Keyword(s):  
Eye Movements ◽  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Reaction Times ◽  
Saccadic Eye Movements ◽  
Neuronal Population ◽  
Single Unit Activity ◽  
Cortical Control ◽  
Posterior Parietal ◽  
Saccadic Reaction Times

ABSTRACTAbnormal saccadic eye movements can serve as biomarkers for patients with several neuropsychiatric disorders. To investigate cortical control mechanisms of saccadic responses, the common marmoset (Callithrix jacchus) is a promising non-human primate model. Their lissencephalic brain allows for accurate targeting of homologues of sulcal areas in the macaque brain. Here we recorded single unit activity in the posterior parietal cortex of two marmosets using chronic microelectrode arrays, while the monkeys performed a saccadic task with Gap trials (stimulus onset lagged fixation point offset by 200ms) interleaved with Step trials (fixation point disappeared when the peripheral stimulus appeared). Both marmosets showed a gap effect—shorter saccadic reaction times (SRTs) in Gap vs. Step trials. On average, stronger gap-period response across the entire neuronal population preceded shorter SRTs on trials with contralateral targets, although this correlation was stronger among the 15% ‘gap neurons’, which responded significantly during the gap. We also found 39% ‘target neurons’ with significant visual target-related responses, which were stronger in Gap trials and correlated with the SRTs better than the remaining cells. Compared with slow saccades, fast saccades were preceded by both stronger gap-related and target-related response in all PPC neurons, regardless of whether such response reached significance. Our findings suggest that the PPC in the marmoset contains an area that is involved in the modulation of saccadic preparation and plays roles comparable to those of area LIP in macaque monkeys in eye movements.SIGNIFICANCE STATEMENTAbnormal saccadic eye movements can serve as biomarkers for different neuropsychiatric disorders. So far, processes of cerebral cortical control of saccades are not fully understood. Non-human primates are ideal models for studying such processes, and the marmoset is especially advantageous since their smooth cortex permits laminar analyses of cortical microcircuits. Using electrode arrays implanted in the posterior parietal cortex of marmosets, we found neurons responsive to key periods of a saccadic task in a manner that contribute to cortical modulation of saccadic preparation. Notably, this signal was correlated with subsequent saccadic reaction times and was present in the entire neuronal population. We suggest that the marmoset model will shed new light on the cortical mechanisms of saccadic control.

scholarly journals Integration of target and hand position signals in the posterior parietal cortex: effects of workspace and hand vision

2012 ◽  
Vol 108 (1) ◽  
pp. 187-199 ◽  
Author(s):  
Christopher A. Buneo ◽  
Richard A. Andersen
Keyword(s):  
Parietal Cortex ◽  
Visual Cues ◽  
Posterior Parietal Cortex ◽  
Single Cells ◽  
Arm Movement ◽  
Movement Planning ◽  
Hand Position ◽  
Position Information ◽  
Limb Position ◽  
Posterior Parietal

Previous findings suggest the posterior parietal cortex (PPC) contributes to arm movement planning by transforming target and limb position signals into a desired reach vector. However, the neural mechanisms underlying this transformation remain unclear. In the present study we examined the responses of 109 PPC neurons as movements were planned and executed to visual targets presented over a large portion of the reaching workspace. In contrast to previous studies, movements were made without concurrent visual and somatic cues about the starting position of the hand. For comparison, a subset of neurons was also examined with concurrent visual and somatic hand position cues. We found that single cells integrated target and limb position information in a very consistent manner across the reaching workspace. Approximately two-thirds of the neurons with significantly tuned activity (42/61 and 30/46 for left and right workspaces, respectively) coded targets and initial hand positions separably, indicating no hand-centered encoding, whereas the remaining one-third coded targets and hand positions inseparably, in a manner more consistent with the influence of hand-centered coordinates. The responses of both types of neurons were largely invariant with respect to the presence or absence of visual hand position cues, suggesting their corresponding coordinate frames and gain effects were unaffected by cue integration. The results suggest that the PPC uses a consistent scheme for computing reach vectors in different parts of the workspace that is robust to changes in the availability of somatic and visual cues about hand position.

Posterior parietal cortex mediates encoding processes in change blindness

2009 ◽  
Author(s):  
Philip Tseng ◽  
Cassidy Sterling ◽  
Adam Cooper ◽  
Bruce Bridgeman ◽  
Neil G. Muggleton ◽  
...  
Keyword(s):  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Change Blindness ◽  
Posterior Parietal

The Grasp Cell Hypothesis: Near-miss effect points to common neurological machinery in posterior parietal cortex for controllable objects and concepts

2018 ◽  
Author(s):  
Imogen M Kruse
Keyword(s):  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Near Miss ◽  
Illusion Of Control ◽  
Gambling Behaviour ◽  
Drug Seeking ◽  
Spatial Influence ◽  
Reward Probability ◽  
Posterior Parietal ◽  
Action Value

The near-miss effect in gambling behaviour occurs when an outcome which is close to a win outcome invigorates gambling behaviour notwithstanding lack of associated reward. In this paper I postulate that the processing of concepts which are deemed controllable is rooted in neurological machinery located in the posterior parietal cortex specialised for the processing of objects which are immediately actionable or controllable because they are within reach. I theorise that the use of a common machinery facilitates spatial influence on the perception of concepts such that the win outcome which is 'almost complete' is perceived as being 'almost within reach'. The perceived realisability of the win increases subjective reward probability and the associated expected action value which impacts decision-making and behaviour. This novel hypothesis is the first to offer a neurological model which can comprehensively explain many empirical findings associated with the near-miss effect as well as other gambling phenomena such as the ‘illusion of control’. Furthermore, when extended to other compulsive behaviours such as drug addiction, the model can offer an explanation for continued drug-seeking following devaluation and for the increase in cravings in response to perceived opportunity to self-administer, neither of which can be explained by simple reinforcement models alone. This paper therefore provides an innovative and unifying perspective for the study and treatment of behavioural and substance addictions.

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