Invariance of Functional Characteristics to Task Difference at Low-Level and High-Level Areas in the Ventral Visual Pathway

Tasks with stimuli are often used for the examination of stimulus-related functional characteristics of brain areas. However, the task can affect the response to a stimulus. Repetition suppression is a phenomenon that can be used to probe neuronal properties using macroscale functional magnetic resonance imaging (fMRI). The use of repetition suppression as an investigative tool to assess functional characteristics warrants the investigation of the invariance of repetition suppression to a given task. In this study, we examined repetition suppression using images of faces during different tasks. We found that the task difference did not change the response patterns related to repetition suppression in high-level areas and the primary visual area while it changed amplitudes of fMRI response to the visual stimuli. The result suggests that the repetition-suppression phenomenon is robust compared with the amplitude of fMRI response, and functional characteristics can be examined using the repetition-suppression phenomenon even under the condition that fMRI response is varied by task difference.

Cross-modal connectivity of the secondary auditory cortex with higher visual area in the congenitally deaf—A case study

It is well known that auditory cortical areas are activated by visual stimulation in the deaf. However, it is not known whether the information enters from the primary visual area or high-level visual areas. In this study, we used visual language stimulation to examine visual-auditory functional connectivity. For this, we used functional magnetic resonance imaging (fMRI) in a congenitally deaf subject to localize areas in the auditory cortex that showed cross-modal reorganization for the processing of visual language inputs and estimate areas in the visual ventral stream, from which language signal inputs enter the auditory areas in the congenitally deaf. We found that the anterior region of the secondary auditory cortex in the superior temporal gyrus showed language-specific activation and that the visual inputs into the area were from the fusiform gyrus, which is a high-level visual area.

Eye Movements Provide Inhibitory Inputs to the Occipito-Temporal Region

Eye movements play an important role in attention and visual processing. However, the manner in which eye move-ments are involved in object processing is not clear. The aim of this study is to examine the effects of eye movements on object-processing areas in the occipito-temporal region. Eye movements are always accompanied by visual perception;therefore, the effects of eye movements on object-processing areas in which visual object information is sent via eye movements instead of via retinal inputs of visual images must be measured. For this purpose, response to an eye- drawing stimulation in subjects who drew pictures of faces or buildings by their moving eyes under closed-eye condi-tions was measured by functional magnetic resonance imaging. Functional areas in the occipito-temporal region showed negative responses to the eye-drawing stimulation, and the pattern of negative activation maps in the region was almost the same as that of positive activation maps observed after visual image stimulation. Responses in cate-gory-selective area showed category dependency to the eye-drawing stimulation. This suggests that eye movements provide inhibitory inputs to the object-processing areas in the occipito-temporal region, and these inputs may modulate visual inputs to these areas coming through the retina in the visual perception process.