Yoshiaki Someya

Hand shape selection in pantomimed grasping: Interaction between the dorsal and the ventral visual streams and convergence on the ventral premotor area†

In visually guided grasping, possible hand shapes are computed from the geometrical features of the object, while prior knowledge about the object and the goal of the action influence both the computation and the selection of the hand shape. We investigated the system dynamics of the human brain for the pantomiming of grasping with two aspects accentuated. One is object recognition, with the use of objects for daily use. The subjects mimed grasping movements appropriate for an object presented in a photograph either by precision or power grip. The other is the selection of grip hand shape. We manipulated the selection demands for the grip hand shape by having the subjects use the same or different grip type in the second presentation of the identical object. Effective connectivity analysis revealed that the increased selection demands enhance the interaction between the anterior intraparietal sulcus (AIP) and posterior inferior temporal gyrus (pITG), and drive the converging causal influences from the AIP, pITG, and dorsolateral prefrontal cortex to the ventral premotor area (PMv). These results suggest that the dorsal and ventral visual areas interact in the pantomiming of grasping, while the PMv integrates the neural information of different regions to select the hand posture. The present study proposes system dynamics in visually guided movement toward meaningful objects, but further research is needed to examine if the same dynamics is found also in real grasping. Hum Brain Mapp, 2012.

An fMRI analysis of the efficacy of Euler diagrams in logical reasoning

We compared participant performance and brain activation changes during a syllogism-solving task with and without Euler diagrams, using functional magnetic resonance imaging (fMRI). Our experiment showed that when Euler diagrams were present, (i) response times in the task were significantly shorter than those in the usual reasoning task comprising only sentences, and (ii) the magnitude of activation in the left middle frontal gyrus (near BA 10), left inferior PFC (near BA 47), and left dorsal PFC (BA 6) was reduced. Result (i) provides evidence for the occurrence of cognitive offloading even when participants handle information of both sentences and diagrams in reasoning tasks. Result (ii) suggests that complex processes of inferences can be replaced by simple diagram manipulation. It is argued that cognitive details that are not fully specified by behavioral studies can be made salient using neuroscientific methods.

Subsequent memory-dependent EEG θ correlates to parahippocampal blood oxygenation level-dependent response

The 4–12 Hz (&thgr; rhythm)-dependent neural dynamics play a fundamental role in the memory formation of the rat hippocampus. Although the power of human scalp electroencephalography &thgr; (EEG &thgr;) is known to be associated with a hippocampus-dependent memory encoding, it remains unclear whether the human hippocampus uses &thgr; rhythm. In this study, we aim to identify the scalp EEG &thgr;-related neural regions during memory encoding by using a simultaneous EEG–functional magnetic resonance imaging recording. We showed that the parahippocampal and the medial frontal and posterior regions were significantly correlated to subsequent memory-dependent EEG &thgr; power. This evidence suggests that the human parahippocampal region and associated structures use &thgr; rhythm during hippocampal memory encoding as in rodents.

The Neural Basis of Typewriting: A Functional MRI Study

To investigate the neural substrate of typewriting Japanese words and to detect the difference between the neural substrate of typewriting and handwriting, we conducted a functional magnetic resonance imaging (fMRI) study in 16 healthy volunteers. All subjects were skillful touch typists and performed five tasks: a typing task, a writing task, a reading task, and two control tasks. Three brain regions were activated during both the typing and the writing tasks: the left superior parietal lobule, the left supramarginal gyrus, and the left premotor cortex close to Exner’s area. Although typing and writing involved common brain regions, direct comparison between the typing and the writing task revealed greater left posteromedial intraparietal cortex activation in the typing task. In addition, activity in the left premotor cortex was more rostral in the typing task than in the writing task. These findings suggest that, although the brain circuits involved in Japanese typewriting are almost the same as those involved in handwriting, there are brain regions that are specific for typewriting.

Involvement of low-level visual areas in hemispheric superiority for face processing.

Previous studies on laterality in face processing have indicated superiority of the right hemisphere in discriminating and recognizing faces; however, the reasons for this feature are poorly understood. We employed functional MRI (fMRI) to elucidate the origin of this feature and used a paired-stimulus paradigm in which face pairs were presented unilaterally at the left or right visual hemifield of the participants. Each face in a pair was at a different position in the visual field. Refractory suppression in the fMRI response was observed bilaterally at the fusiform face area (FFA) for the same face pairs when pictures were presented in the left visual hemifield. In contrast, suppression was observed bilaterally at the FFA for the different as well as for the same face pairs when pictures were presented in the right visual hemifield. This pattern indicated inferior discrimination ability for paired stimuli presented to the right visual hemifield. These observations, along with changes in bilaterally interlocked responses at the FFA, suggest that low-level visual areas, and not high-level face areas, are strongly associated with the superiority of the right hemisphere in face processing.

Temporal feature of BOLD responses varies with temporal patterns of movement.

Which brain sites represent the final form of motor commands that encode temporal patterns of muscle activities? Here, we show the possible brain sites which have activity equivalent to the motor commands with functional magnetic resonance imaging (fMRI). We hypothesized that short-temporal patterns of movements or stimuli are reflected in blood-oxygenation-level-dependent (BOLD) responses and we searched for regions representing the response. Participants performed two temporal patterns of tapping and/or listened to the same patterns of auditory stimuli in a 3T fMRI. The patterns were designed to have the same number (11) of events and the same duration, but different temporal distribution of events. The 11 events were divided into two parts (10 repetitive taps and one stand-alone tap) and the interval of the two parts was 3s. The two patterns had reverse order of the two parts. The results revealed that different temporal patterns of auditory stimuli were represented in different temporal features of BOLD responses in the bilateral auditory cortex, whereas different temporal patterns of tapping were reflected in contralateral primary motor cortex and the ipsilateral anterior cerebellum. In bilateral premotor cortex, supplementary motor area, visual cortex, and posterior cerebellum, task-related BOLD responses were exhibited, but their responses did not reflect the temporal patterns of the movement and/or stimuli. One possible explanation is that the neuronal activities were similar for the two patterns in these regions. The sensitivity of the BOLD response to the temporal patterns reflects local differences in functional contributions to the tasks. The present experimental design and analysis may be useful to reveal particular brain regions that participate in multiple functions.

Correction: The Neural Basis of Typewriting: A Functional MRI Study

Fig 1 is an incorrect, previous version. Please view the corrected Fig 1 here. Fig 1 A diagram of the assumptions underlying the present analysis.

BOLD signal reflects temporal patterns of movement

Impulsivity is often expressed as aggressive behaviour. It is associated with poor self-control which can be a major portion of many diseases if it reaches pathological levels. It can be emerged in several forms such as rapid decision making, inability to tolerate a delay of enjoyment and tendency to terminate chains of responses prematurely. Tolerance to delay of reward has been proposed as self-control. We investigated the involvement of delay duration and the amount of reinforcement in a T-maze based impulsivity task. After acclimatization, rats were trained to choose between a single food pellet delivered immediately and four or eight pellets delivered after delay. The percent of animals that chose the arm baited with large reward were signified as response and evaluated compared to the development and sort of trials. The results show an enhancement of responses by enlargement in size of reward in animals. The responses were slowly declined with increasing delay time, this was significant in 10–30 s. To clarify the details more studies can be conducted by using of this animal model.