Hironori Nakatani

The neural basis of intuitive best next-move generation in board game experts.

Compared with amateurs, expert shogi players show specific brain activation patterns. The superior capability of cognitive experts largely depends on quick automatic processes. To reveal their neural bases, we used functional magnetic resonance imaging to study brain activity of professional and amateur players in a board game named shogi. We found two activations specific to professionals: one in the precuneus of the parietal lobe during perception of board patterns, and the other in the caudate nucleus of the basal ganglia during quick generation of the best next move. Activities at these two sites covaried in relevant tasks. These results suggest that the precuneus-caudate circuit implements the automatic, yet complicated, processes of board-pattern perception and next-move generation in board game experts.

Transient Synchrony of Distant Brain Areas and Perceptual Switching in Ambiguous Figures

We studied the relationship between perceptual switching in the Necker cube and long-distance transient phase synchronization in EEG. Transient periods of response related synchrony between parietal and frontal areas were observed. They start 800–600, ms prior to the switch response and occur in pairs. Four types of pairs could be distinguished, two of which are accompanied by transient alpha band activity in the occipital area. The results indicate that perceptual switching processes involve parietal and frontal areas; these are the ones that are normally associated with various cognitive processes. Sensory information in the visual areas is involved in some, but not in all, of switching processes. The intrinsic variability, as well as the participating areas, points to the role of strategic cognitive processes in perceptual switching.

Individual differences in perceptual switching rates; the role of occipital alpha and frontal theta band activity

Prolonged presentation of visually ambiguous figures leads to perceptual switching. Individual switching rates show great variability. The present study compares individuals with high versus low switching rates by investigating human scalp electroencephalogram and blink rates. Eight subjects viewed the Necker cube continuously and responded to perceptual switching by pressing a button. Frequent switchers showed characteristic occipital alpha and frontal theta band activity prior to a switch, whereas infrequent switchers did not. The alpha activity was specific to switching, the theta activity was generic to perceptual processing conditions. A negative correlation was observed between perceptual switching and blink rates. These results suggest that the ability to concentrate attentional effort on the task is responsible for the differences in perceptual switching rates

Antecedent occipital alpha band activity predicts the impact of oculomotor events in perceptual switching

Oculomotor events such as blinks and saccades transiently interrupt the visual input and, even though this mostly goes undetected, these brief interruptions could still influence the percept. In particular, both blinking and saccades facilitate switching in ambiguous figures such as the Necker cube. To investigate the neural state antecedent to these oculomotor events during the perception of an ambiguous figure, we measured the human scalp electroencephalogram (EEG). When blinking led to perceptual switching, antecedent occipital alpha band activity exhibited a transient increase in amplitude. When a saccade led to switching, a series of transient increases and decreases in amplitude was observed in the antecedent occipital alpha band activity. Our results suggest that the state of occipital alpha band activity predicts the impact of oculomotor events on the percept.

Perceived moral traits of others differentiate the neural activation that underlies inequity-aversion

We have a social preference to reduce inequity in the outcomes between oneself and others. Such a preference varies according to others. We performed functional magnetic resonance imaging during an economic game to investigate how the perceived moral traits of others modulate the neural activities that underlie inequity-aversion. The participants unilaterally allocated money to three partners (good, neutral, and bad). During presentation of the good and neutral partners, the anterior region of the rostral medial frontal cortex (arMFC) showed increased functional connectivity with the caudate head and the anterior insula, respectively. Following this, participants allocated more money to the good partner, and less to the bad partner, compared with the neutral partner. The caudate head and anterior insula showed greater activation during fair allocation to the good and unfair allocation to the neutral partners, respectively. However, these regions were silent during allocations to the bad partner. Therefore, the arMFC-caudate/insula circuit encompasses distinct neural processes that underlie inequity-aversion in monetary allocations that the different moral traits of others can modulate.

Sense of Accomplishment Is Modulated by a Proper Level of Instruction and Represented in the Brain Reward System.

Problem-solving can be facilitated with instructions or hints, which provide information about given problems. The proper amount of instruction that should be provided for learners is controversial. Research shows that tasks with intermediate difficulty induce the largest sense of accomplishment (SA), leading to an intrinsic motivation for learning. To investigate the effect of instructions, we prepared three instruction levels (No hint, Indirect hint, and Direct hint) for the same insight-problem types. We hypothesized that indirect instructions impose intermediate difficulty for each individual, thereby inducing the greatest SA per person. Based on previous neuroimaging studies that showed involvement of the bilateral caudate in learning and motivation, we expected SA to be processed in this reward system. We recruited twenty-one participants, and investigated neural activations during problem solving by functional magnetic resonance imaging (fMRI). We confirmed that the Indirect hint, which imposed intermediate difficulty, induced the largest SA among the three instruction types. Using fMRI, we showed that activations in the bilateral caudate and anterior cingulate cortex (ACC) were significantly modulated by SA. In the bilateral caudate, the indirect hint induced the largest activation, while the ACC seemed to reflect the difference between correct and incorrect trials. Importantly, such activation pattern was independent of notations (number or letter). Our results indicate that SA is represented in the reward system, and that the Indirect instruction effectively induces such sensation.

Neural Synchrony for Expert Memory in Shogi (Japanese Chess) Players

Experts in most domains show superior memory performances for domain-specific stimuli. Psychological studies proposed that chunk-based processing is a key mechanism of cognitive expertise and superior memory performances of experts are natural consequences of chunk-based processing. A neuroimaging study has shown that chunks are stored in the temporal lobe. On the other hand, brain dynamics underlying chunk-based processing is poorly understood. With shogi (Japanese chess), we investigated neural synchrony underlying working memory of shogi players. We found that neural phase synchrony between the frontal and the temporal areas was associated with memory retention of expert players. The result indicates that synchronized interaction between frontal executive area and temporal chunk area realizes chunk-based processing.

Expertise-related differences in EEG activity during working memory for shogi piece positions

The ability to estimate elapse time is crucial to anticipate upcoming events and prepare appropriate actions. In this study, we examined whether this ability improved with training on a reaction-time (RT) task in which human subjects were required to initiate wrist movements quickly after a ‘Go’ signal. The probability that the Go signal would occur (i.e., the hazard rate) increased with the amount of time that elapsed (e.g., 1–2 s) before the onset of the signal (i.e., the foreperiod). We calculated a blurred version of hazard rate (i.e., subjective hazard rate), which was formalized based on the assumption that uncertainty in time estimation scales with time (i.e., Weber’s law). The waveform of the subjective hazard function depended on the Weber fraction for time estimation. Subjects performed the task for 480 trials/day for 12 days. Reaction time decreased as the duration of the foreperiod increased, suggesting that subjects estimated elapsed time and calculated time-dependent probability associated with the Go signal. Training affected the pattern of RT decrease. The decrease became consistent, independent of the foreperiod, throughout training. Reaction time was inversely related to, and well fit by, a weighted sum of subjective hazard rates. The fitting procedure revealed that the consistent decrease in RT involved a decrease in the Weber fraction. The results indicate that the ability to process time improves with experience using elapsed time to anticipate the onset of behaviorally relevant events and to prepare appropriate actions.

Cerebellar activation during Check-mate task execution

Cerebellum is involved in the motor control system to generate smooth and accurate motor command. The acquisition of the cerebellar circuit is achieved by repetitive non-declarative learning. We would like to expand the cerebellar function to thinking process, especially intuitive thinking. To verify our hypothesis, we employed Japanese-chess, “SHOGI”, and its players from trained amateur to professional player. Psychophysical experiments revealed optimal time to answer given checkmate task intuitively. Furthermore, changing rule of the SHOGI affects correct answer ratio depending to their original SHOGI experience. Then we measured cerebellar BOLD using 4T-MRI system during previously obtained condition. Their both lateral hemisphere cerebellar BOLD was selectively increased during checkmate task, not control conditions.These results imply that intuitive thinking, the answer is given within short time and semi-automatically, may use cerebellar circuitry which is acquired repetitive training. We will further investigate the analogy between cerebellar motor control and the intuition.