Neuronal population coding of continuous and discrete quantity in the primate posterior parietal cortex

The present study was designed to investigate whether the rat posterior parietal cortex is involved in the perception and the representation of the auditory space. We recorded single neural activity in the posterior parietal cortex of rats that performed a directional delayed nonmatching-to-sample task. In the task, cue tones were presented in one of six speakers that were placed symmetrically around the rats. “Familiar tones” were those repeatedly used in the course of behavioral training. Novel tones were presented only during the unit recording time and less frequently used (e.g., only once in alternate weeks). The responses of the posterior parietal cortex neurons were typically tested with familiar cue tones while the rats were situated in a particular geomagnetic orientation. The same cells were further tested while the rats were reoriented by 180°, or by novel cue tones. As the task included a delay period, in which the cue tone was removed, the rats had to maintain the directional information of the cue tones during this period to maximize the reward rates. A well-trained rat could perform the task with 85% success. We found two major types of neurons intermixed in the rat posterior parietal cortex. One type ( n = 14) mainly discriminated the direction of the cue tones, whereas the other ( n = 36) carried a mnemonic value of the cue tones while the tones were removed. The former responded only during the cue tone period (discriminatory neurons), whereas the latter responded during the cue tone period and the delay period (mnemonic neurons). These cells also exhibited broad directional tuning. The results agreed with previous studies, suggesting that a population coding scheme exists in the posterior parietal cortex. When the cells were tested with novel tones or when the rats were rotated through 180°, the vast majority of the cells exhibited a directional tuning similar to those under the control conditions. Three quarters (18/24) of the cells that exhibited a mnemonic characteristic persisted in their directional preference when the rat's orientation was changed (12/17 neurons) or when an unfamiliar auditory stimulus was used (6/7 neurons). Half of the discriminatory neurons (4/8 neurons) persisted in their directional preference. These results, consistent with previous behavioral studies, suggest an allocentric representation of the auditory processing in this area. Furthermore, when the rat was reoriented or an unfamiliar cue tone was used, both the average and peak directional responses were enhanced in more than half of the mnemonic or discriminatory neurons. These results support the frequency-dependent neocortical gating hypothesis of the entorhinal hippocampal loop.

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

eLife ◽

10.7554/elife.61646 ◽

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.

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Adaptation to Visuomotor Rotation Through Interaction Between Posterior Parietal and Motor Cortical Areas

Journal of Neurophysiology ◽

10.1152/jn.90834.2008 ◽

2009 ◽

Vol 102 (5) ◽

pp. 2921-2932 ◽

Cited By ~ 95

Author(s):

Hirokazu Tanaka ◽

Terrence J. Sejnowski ◽

John W. Krakauer

Keyword(s):

Motor Cortex ◽

Parietal Cortex ◽

Posterior Parietal Cortex ◽

Motor Units ◽

Population Coding ◽

Learning Curves ◽

Visuomotor Rotation ◽

Tuning Curves ◽

Posterior Parietal ◽

Psychophysical Studies

Studying how motor adaptation to visuomotor rotation for one reach direction generalizes to other reach directions can provide insight into how visuomotor maps are represented and learned in the brain. Previous psychophysical studies have concluded that postadaptation generalization is restricted to a narrow range of directions around the training direction. A population-coding model that updates the weights between narrow Gaussian-tuned visual units and motor units on each trial reproduced experimental trial-by-trial learning curves for rotation adaptation and the generalization function measured postadaptation. These results suggest that the neurons involved in rotation adaptation have a relatively narrow directional tuning width (∼23°). Population coding models with units having broader tuning functions (such as cosine tuning in motor cortex and Gaussian sum in the cerebellum) could not reproduce the narrow single-peaked generalization pattern. Visually selective neurons with narrow Gaussian tuning curves have been identified in posterior parietal cortex, making it a possible site of adaptation to visuomotor rotation. We propose that rotation adaptation proceeds through changes in synaptic weights between neurons in posterior parietal cortex and motor cortex driven by a prediction error computed by the cerebellum.

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

10.1101/737312 ◽

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.

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

10.1101/2020.07.27.223636 ◽

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.

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Posterior parietal cortex mediates encoding processes in change blindness

PsycEXTRA Dataset ◽

10.1037/e520562012-977 ◽

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

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

10.31234/osf.io/4awrz ◽

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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