Yoshimi Ohgami

Waiting to perceive: Reward or punishment?

Neurobiological accounts of the dopaminergic reward system and psychophysiological explanations of the error-related negativity (ERN) both emphasize the comparison of expected versus actual outcome for voluntary actions. The stimulus-preceding negativity (SPN) constitutes a valuable index of that expectation, in that it has high temporal resolution and its anatomical, cognitive and affective correlates have been reasonably well characterized. This review links established findings regarding the SPN to current research on the dorsal and ventral attention systems, somatic marker hypothesis, ERN, the reward system and relevant neurological and psychiatric findings. Special emphasis is given to the pre-feedback SPN and its origin within anterior insular cortex.

The role of the right anterior insular cortex in the right hemisphere preponderance of stimulus-preceding negativity (SPN): an fMRI study.

The stimulus-preceding negativity (SPN) is an event-related potential that reflects emotional and perceptual anticipation. The SPN is characterized by a right hemisphere preponderance in amplitude, and previous studies suggest that activity in the insular cortex might contribute to the amplitude of the SPN. Although the insula might contribute to the SPNs occurrence, the exact role of the insula in the pattern of SPN right hemisphere dominance remains unclear. In the present study, we manipulated task difficulty and brain activation was measured using event-related fMRI, to examine the relationship between insula functioning and the right hemisphere preponderance of the SPN. Twenty-three participants performed a time estimation task, in which they had to press a button when they thought a predetermined time had elapsed. Three seconds after pressing the button, a feedback stimulus was presented, informing subjects as to whether their response was correct, too early, or too late. There were four experimental conditions: easy, moderate, difficult, and no feedback. The fMRI results showed significantly increased activation in the bilateral insular cortex during the pre-feedback anticipation phase, in which the subjects prepare to pay attention to the occurrence of feedback stimuli. In addition, in the Difficult-Easy and Difficult-Moderate contrasts, significantly increased activations of the right anterior insula were demonstrated, suggesting the possibility that this area does underlie the SPN right hemisphere preponderance. Because the right anterior insula is related to awareness of viscerosensory information, the SPN right hemisphere preponderance might itself be related to the awareness of interoceptive information that precedes feedback stimuli.

Neural correlates of phoneme-to-grapheme conversion.

In writing to dictation, one mode of language processing is based on the knowledge of how to convert speech sounds to the corresponding letters, namely, phoneme-to-grapheme conversion (phonological mode). Little is known about the neural substrates of the phoneme-to-grapheme conversion. Our study aims to clarify the neural substrates of phoneme-to-grapheme conversion in writing to dictation using functional magnetic resonance imaging. We employed Japanese as the stimulus language because in Japanese, one phoneme is represented by one grapheme (kana) and vice versa. Functional magnetic resonance imaging revealed that the left premotor, extending into Brocas area was activated. The present results suggested that the frontal region is required for the conversion of phonemes to graphemes in writing to dictation.

Activation of insular cortex and subcortical regions related to feedback stimuli in a time estimation task: An fMRI study

We used functional magnetic resonance imaging to investigate brain activity related to motivational function of informative feedback stimuli in a time estimation task. In that task, subjects pressed a button as a response 3 s after a cue stimulus; a visual feedback stimulus was presented 2 s after the response. In a true feedback condition, subjects received true information (informative feedback) about their time-estimation performance. In the false feedback condition, the same visual signs were used, but they were presented randomly. Therefore, they were not related to actual performance. In the 20 subjects examined, higher hemodynamic responses were identified in the insular cortex, the thalamus, and the striatum by comparing the true feedback condition to the false feedback condition. The time estimation performance and subjective score on motivation were also markedly higher in the true feedback condition. The anterior insular cortex and striatal regions are known to be involved in motivational and reward processing. Therefore, the hemodynamic responses observed in this study suggest that the motivational function of the feedback information is a crucial factor for behavioral learning; it is considered that the informative feedback might serve as an implicit reward for humans.

Source analysis of stimulus-preceding negativity constrained by functional magnetic resonance imaging.

The stimulus-preceding negativity (SPN) is an event-related potential (ERP) reflecting anticipation. The anterior insular cortex is assumed to be one of the physiological sources of the SPN. However, the precise neural substrates of the SPN have yet to be confirmed. We therefore performed separate functional magnetic resonance imaging (fMRI) and ERP studies using the same time estimation task, followed by fMRI-constrained ERP source analysis. Dipole locations were determined by the fMRI results, while the time courses of dipole activities were modeled by the ERP data. Analysis revealed that the right anterior insula was significantly activated before delivery of the feedback stimulus, whereas the left anterior insula was not, and that the SPN mainly arose from four groups of brain regions related to, respectively: (1) the salience network, (2) reward expectation, (3) perceptual anticipation, and (4) arousal. The results suggest that the SPN pertains to multiple brain functions with complex interactions.

Facial, verbal, and symbolic stimuli differently affect the right hemisphere preponderance of stimulus-preceding negativity.

The present study investigated whether the right hemisphere preponderance of stimulus-preceding negativity (SPN) was affected by different categories of visual feedback stimulus. A time estimation task was performed with facial, verbal, symbolic, and no-feedback conditions. A principal component analysis identified an early component of SPN in addition to a late component that was morphologically similar to the original SPN. Motivational scores in the verbal and facial conditions were higher than that in the symbolic condition. Significant right hemisphere preponderance of the late SPN was observed in the symbolic condition but not in the verbal condition, whereas right hemisphere preponderance of the early SPN was observed in the facial condition. The right hemisphere preponderance was influenced by the category of visual feedback stimulus through stimulus-related activation and the effect of the motivational level.

24. The contribution of the right insula and the right frontal operculum to the EEG potential reflecting emotional anticipation

21. Time course of frontal lobe activation in schizophrenia: A multi-task study using two channel near-infrared spectroscopy— Masao Iwase, Michiyo Azechi, Koji Ikezawa, Ryouhei Ishii, Hidetoshi Takahashi, Takayuki Nakahachi, Leonides Canuet, Ryu Kurimoto, Hiroaki Kazui, Motoyuki Fukumoto, Naomi Iike, Kazutaka Ohi, Yuka Yasuda, Ryota Hashimoto, Masatoshi Takeda (Department of Psychiatry, Osaka University, Suita, Japan)