Neuronal categorization and discrimination of social behaviors in primate prefrontal cortex.

It has been implied that primates have an ability to categorize social behaviors between other individuals for the execution of adequate social-interactions. Since the lateral prefrontal cortex (LPFC) is involved in both the categorization and the processing of social information, the primate LPFC may be involved in the categorization of social behaviors. To test this hypothesis, we examined neuronal activity in the LPFC of monkeys during presentations of two types of movies of social behaviors (grooming, mounting) and movies of plural monkeys without any eye- or body-contacts between them (no-contacts movies).

Similar prefrontal cortical activities between general fluid intelligence and visuospatial working memory tasks in preschool children as revealed by optical topography.

General fluid intelligence (gF) is a major component of intellect in both adults and children. Whereas its neural substrates have been studied relatively thoroughly in adults, those are poorly understood in children, particularly preschoolers. Here, we hypothesized that gF and visuospatial working memory share a common neural system within the lateral prefrontal cortex (LPFC) during the preschool years (4-6 years).

Functional columns in the primate prefrontal cortex revealed by optical imaging in vitro.

Although the functional column has been implicated in the dorsolateral prefrontal cortex (DLPFC) of primates, its dynamics and even existence are still uncertain. We performed optical recording with a voltage-sensitive dye (RH482) in brain slices obtained from the principal sulcal region (area 46) of macaque monkeys. Columnar activity was evoked by electrical stimulation of the middle layer (lower layer III or layer IV); this activity consisted of two components: probably action potentials and excitatory postsynaptic potentials.

Involvement of the lateral prefrontal cortex in conditional suppression of gaze shift.

Conditional execution and suppression of gaze shift are important in everyday life. To examine the possible involvement of the lateral prefrontal cortex (LPFC) in this process, we induced a local and reversible inactivation by injecting muscimol into 66 sites within the LPFC of monkeys and examined muscimol's effect on their performance in an oculomotor Go/No-Go task. This task required a subject to execute (Go) or suppress (No-Go) its gaze toward a target location in response to an instructional visual cue.

Plasticity of the primate prefrontal cortex.

Cortical plasticity refers to flexible and long-lasting changes in neuronal circuitry and information processing, which is caused by learning and experience. Although cortical plasticity can be observed in every cortex of the brain, the plasticity of the prefrontal cortex (PFC) is particularly important because the PFC is involved in various cognitive functions, and its plasticity could lead to adaptive changes in the use of other brain regions. Cortical plasticity occurs at several levels, from functional molecules to the organization of large areas of the brain.

Prediction of relative and absolute time of reward in monkey prefrontal neurons.

We studied single-neuron activity in the monkey dorsolateral prefrontal cortex during a saccade task, in which correct responses were rewarded after a delay of 0.5 or 1.5 s in one trial-block, and after 1.

Developmental fractionation of working memory and response inhibition during childhood.

The lateral prefrontal cortex (LPFC) plays a major role in both working memory (WM) and response inhibition (RI), which are fundamental for various cognitive abilities. We explored the relationship between these LPFC functions during childhood development by examining the performance of two groups of children in visuospatial and auditory WM tasks and a go/no-go RI task. In the younger children (59 5- and 6-year-olds), performance on the visuospatial WM task correlated significantly with that in the auditory WM task.

Rule-dependent shifting of sensorimotor representation in the primate prefrontal cortex.

When we react to the outer world, perceived sensory information is frequently memorized over a temporal interval then transformed into a motor command based on a behavioural rule. In this type of memory-based sensorimotor transformation, working memory is considered to play an important role. It has been suggested that the lateral prefrontal cortex is involved in the process of the working memory.

Contrasting effects of reward expectation on sensory and motor memories in primate prefrontal neurons.

The value of reward obtained with successful behavior is important for guiding purposeful behavior. The lateral prefrontal cortex (LPFC) has been implicated in working memory that guides goal-directed behavior. However, mechanism that integrates the reward value into the working memory for goal-directed behavior is not understood.

Neural representation of response category and motor parameters in monkey prefrontal cortex.

Conditional motor behavior, in which the relationship between stimuli and responses changes arbitrarily, is an important component of cognitive motor function in primates. It is still unclear how cognitive processing for conditional motor control determines movement parameters to directly specify motor output. To address this issue, we studied the neuronal representation of motor variables relating to conditional motor control and also directly to the metrics of motor output in prefrontal cortex (PFC).

Neuronal activity representing temporal prediction of reward in the primate prefrontal cortex.

Temporal prediction of future events, especially regarding reward delivery, is critical for controlling/learning purposeful behavior. The dorsolateral prefrontal cortex (DLPFC) has been considered to be involved in behavioral control based on prospective coding for future events, including reward. Thus this area is likely to have a neuronal mechanism responsible for temporal prediction of forthcoming reward.

Context-dependent representation of response-outcome in monkey prefrontal neurons.

For behaviour to be purposeful, it is important to monitor the preceding behavioural context, particularly for factors regarding stimulus, response and outcome. The dorsolateral prefrontal cortex (DLPFC) appears to play a major role in such a context-dependent, flexible behavioural control system, and this area is likely to have a neuronal mechanism for such retrospective coding, which associates response-outcome with the information and/or neural systems that guided the response. To address this hypothesis, we recorded neuronal activity from the DLPFC of monkeys performing memory- and sensory-guided saccade tasks, each of which had two conditions with reward contingencies.

Prefrontal cortical activation associated with working memory in adults and preschool children: an event-related optical topography study.

It is well known that lateral areas of the prefrontal cortex (LPFC) play a central role in working memory (a critical basis of various cognitive functions), but it remains unknown whether the LPFC of children of preschool age is responsible for working memory. To address this issue, we adopted a recently developed non-invasive imaging technique, optical topography (OT), which can potentially be applied to functional mapping in childhood. We firstly examined changes of activity in the LPFC using OT while adult subjects performed an item-recognition task, which requires working memory, under different memory-load conditions.

Properties of delay-period neuronal activity in the primate prefrontal cortex during memory- and sensory-guided saccade tasks.

The dorsolateral prefrontal cortex (DLPFC) is involved in visuospatial short-term (or working) memory. Its cellular basis has been widely examined using the delayed-response paradigm in nonhuman primates. Sustained delay-period activity in DLPFC neurons with directional difference (i.

Neuronal representation of response-outcome in the primate prefrontal cortex.

For flexible control of behaviour, it is important to associate preceding behavioural response with its outcome. Since the dorsolateral prefrontal cortex (dlPFC) plays a major role in such control, it is likely that this area has a neuronal mechanism of coding response-outcome, such as reward/non-reward, based on the nature of the behavioural response made immediately before. To test this hypothesis, we examined neuronal activity in the dlPFC while monkeys performed a variant of the oculomotor delayed-response (ODR) task that had two reward conditions.

Involvement of the dorsolateral prefrontal cortex of monkeys in visuospatial target selection.

To examine the involvement of the dorsolateral prefrontal cortex (PFC) in visuospatial target selection, we induced local, reversible inactivation with muscimol at various sites in the dorsolateral PFC of two rhesus monkeys while they performed oculomotor visual search (OVS) and oculomotor detection (OD) tasks. The OVS task required the subject to select a target stimulus from among distractors and to make a saccade to the target location (target selection was required for correct performance), whereas the OD task only required a saccade to the target (target selection was not required for correct performance). The local injection of muscimol (5 microg, 1 microl) into the dorsolateral PFC induced a specific deficit in the OVS task but not in the OD task.

Neuronal activity representing visuospatial mnemonic processes associated with target selection in the monkey dorsolateral prefrontal cortex.

To investigate how visuospatial mnemonic and target selection processes are represented in the dorsolateral prefrontal cortex (PFC), we studied neuronal attributes of the dorsolateral PFC while monkeys were performing oculomotor delayed visual search (ODVS) and oculomotor delayed-response (ODR) tasks. In the ODVS task, the subject made a memory-guided saccade to a remembered target location that had been presented along with distractors before a delay period; in the ODR task, the target was presented without any distractors. A total of 252 neurons in the dorsolateral PFC showed directional delay-period activity and were divided into two groups; neurons that showed directional delay-period activity predominantly in the ODVS task (n=112), and those that showed such activity similarly in both the ODVS and ODR tasks (n=140).

Working memory of action: a comparative study of ability to selecting response based on previous action in New World monkeys (Saimiri sciureus and Callithrix jacchus).

Working memory of the outcome of one's own action is important for organizing and learning appropriate behaviors in a given condition. To examine whether non-human primates with different neocortical sizes show different abilities regarding working memory for action, the performance of squirrel monkeys (Saimiri sciureus) and common marmosets (Callithrix jacchus) in a kind of delayed-response task was compared. In this task, subjects were required to select a response based on short-term memory of the outcome of their own prior action, which requires working memory of action.