Tadashi Ino

Mental navigation in humans is processed in the anterior bank of the parieto-occipital sulcus

We examined the brain regions which were activated during mental navigation; functional magnetic resonance imaging was performed in 16 right-handed male volunteers. The anterior bank of the parieto-occipital sulcus (APO) was strongly activated in all 16 subjects examined. In group study, the retrosplenial area, the bilateral angular gyrus/occipital cortex junction, the left superior premotor area, the right parahippocampal gyrus, and the right cerebellum were activated commonly across 16 subjects. The APO region activated during mental navigation appeared to be equivalent to the visual area V6A in monkeys and to subserve egocentric spatial processes.

Parieto-frontal networks for clock drawing revealed with fMRI

We studied the neural substrates of clock drawing using functional magnetic resonance imaging in 18 right-handed volunteers. In the test condition, subjects were required to draw the hands of a clock corresponded to the time presented acoustically. In the control task, they drew horizontal and vertical lines after reciting silently the numerals of three figures presented acoustically. In group analyses, comparison between the test and control condition revealed brain areas related to clock drawing; bilateral posterior parietal cortices with a right side dominance, bilateral dorsal premotor areas, the left pre-supplementary motor area, the left ventral prefrontal cortex, the left precentral gyrus, and bilateral cerebellum. In particular, the posterior parietal cortex and the dorsal premotor area, which were strongly activated in all 18 subjects examined in individual analyses, appear to be the main constituent of the parieto-frontal cortical networks for clock drawing.

Somatotopy of corticospinal tract in the internal capsule shown by functional MRI and diffusion tensor images

Using functional MRI and diffusion tensor tractography, we studied the topographical relation of hand and foot fibers of the corticospinal tract within the internal capsule to verify the recent unexpected finding by Holodny et al., who reported that hand fibers are located anterolateral to foot fibers, not anteromedial as is currently believed. The location of hand fibers with respect to foot fibers was anterolateral in four participants, posterolateral in two, and anteromedial in one of seven participants examined. Thus, there was some support for the anterolateral finding of Holodny et al., but interindividual variability was also indicated.

Gender Differences in Brain Activation During Encoding and Recognition of Male and Female Faces

Although behavioral studies have suggested that there are gender differences regarding facial recognition, the neural substrates of these differences have not been fully examined. In order to clarify them, we performed a functional magnetic resonance imaging (fMRI) experiment in which participants encoded and recognized male and female faces. Behaviorally, the facial recognition ability of men and women was similar, and was superior for female faces compared to male faces. At the neural level, widespread areas showed greater responses for men vs. women during the encoding and recognition phase, and several areas, including the hippocampal region, showed greater responses to female vs. male faces during recognition. The reduced activation of women’s brains during encoding and recognition suggests that the relevant neural systems were more efficiently recruited in women than in men.

Longitudinal fMRI study of reading in a patient with letter-by-letter reading.

The present study provides a longitudinal fMRI study of reading 7 days after a hemorrhage in the left basal occipito-temporal region when the patient showed letter-by-letter (LBL) reading, and repeated again 50 days after onset, when his LBL reading had resolved. Direct comparison of the two sessions showed that right homologue of the so called visual word form area (VWFA), as well as a network related to language and verbal working memory, such as the bilateral premotor areas, Brocas area and its right homologue, and the left supplementary motor area were more strongly activated when his LBL reading persisted than when he recovered, whereas perilesional activity around the VWFA and the activity of superior part of the left superior parietal lobule were more strongly activated when he recovered than when his LBL reading persisted. These results suggest that dynamic functional reorganization of the brain was caused in the acute phase and that the increased activation of certain areas in the left superior parietal lobule in addition to the VWFA may be related to recovery from LBL reading.

Recognition and reading aloud of kana and kanji word: an fMRI study.

It has been proposed that different brain regions are recruited for processing two Japanese writing systems, namely, kanji (morphograms) and kana (syllabograms). However, this difference may depend upon what type of word was used and also on what type of task was performed. Using fMRI, we investigated brain activation for processing kanji and kana words with similar high familiarity in two tasks: word recognition and reading aloud. During both tasks, words and non-words were presented side by side, and the subjects were required to press a button corresponding to the real word in the word recognition task and were required to read aloud the real word in the reading aloud task. Brain activations were similar between kanji and kana during reading aloud task, whereas during word recognition task in which accurate identification and selection were required, kanji relative to kana activated regions of bilateral frontal, parietal and occipitotemporal cortices, all of which were related mainly to visual word-form analysis and visuospatial attention. Concerning the difference of brain activity between two tasks, differential activation was found only in the regions associated with task-specific sensorimotor processing for kana, whereas visuospatial attention network also showed greater activation during word recognition task than during reading aloud task for kanji. We conclude that the differences in brain activation between kanji and kana depend on the interaction between the script characteristics and the task demands.

The supramammillary region of the cat sends substance P-like immunoreactive axons to the hippocampal formation and the entorhinal cortex

A combined method of the tracing of WGA-HRP (wheat germ agglutinin-conjugated horseradish peroxidase) and the immunohistochemistry of substance P (SP) showed that many SP-like immunoreactive neurons in the supramammillary nucleus of cat hypothalamus sent their axons to the hippocampal formation. SP-like immunoreactive axons in the hippocampal formation and entorhinal cortex were markedly reduced in number ipsilaterally after placing an electrothermic lesion in the supramammillary region of the hypothalamus.

Brain Activation During Autobiographical Memory Retrieval with Special Reference to Default Mode Network

Recent neuroimaging studies have suggested that brain regions activated during retrieval of autobiographical memory (ABM) overlap with the default mode network (DMN), which shows greater activation during rest than cognitively demanding tasks and is considered to be involved in self-referential processing. However, detailed overlap and segregation between ABM and DMN remain unclear. This fMRI study focuses first on revealing components of the DMN which are related to ABM and those which are unrelated to ABM, and second on extracting the neural bases which are specifically devoted to ABM. Brain activities relative to rest during three tasks matched in task difficulty assessed by reaction time were investigated by fMRI; category cued recall from ABM, category cued recall from semantic memory, and number counting task. We delineated the overlap between the regions that showed less activation during semantic memory and number counting relative to rest, which correspond to the DMN, and the areas that showed greater or less activation during ABM relative to rest. ABM-specific activation was defined as the overlap between the contrast of ABM versus rest and the contrast of ABM versus semantic memory. The fMRI results showed that greater activation as well as less activation during ABM relative to rest overlapped considerably with the DMN, indicating that the DMN is segregated to the regions which are functionally related to ABM and the regions which are unrelated to ABM. ABM-specific activation was observed in the left-lateralized brain regions and most of them fell within the DMN.

Direct projections of non-pyramidal neurons of Ammon's horn to the amygdala and the entorhinal cortex

When WGA-HRP (wheat germ agglutinin-horseradish peroxidase conjugate) was injected into the amygdala (lateral and basolateral amygdaloid nuclei) or entorhinal cortex of the cat, a number of nonpyramidal neurons in Ammons horn were retrogradely labeled. The results indicate that some non-pyramidal neurons in Ammons horn send projection fibers to the amygdala and entorhinal cortex.

Projections from the hippocampal and parahippocampal regions to the entorhinal cortex. An anterograde and retrograde tract-tracing study in the cat

Projections from the hippocampal and parahippocampal regions to the entorhinal cortex (EC) were examined in the cat by anterograde and retrograde tract-tracing with Phaseolus vulgaris leucoagglutinin and cholera toxin B subunit. CA1 fibers to EC were distributed more densely in the medial EC than in the lateral EC; these were seen in all EC layers, but most densely in layers II and III. The septotemporal axis of the area of origin of CA1-EC fibers corresponded to a caudal-to-rostral axis of the area of their termination in the EC. CA2 and CA4 also sent a small number of fibers to the EC. The subiculum sent fibers mainly to the lateral EC; more densely to layers IV-VI than to layers I-III. The septotemporal axis of the area of origin of subiculum-EC fibers corresponded to a caudolateral-to-rostromedial axis of their termination in the EC. Distribution pattern of fibers from the prosubiculum regions close to CA1 or from prosubiculum regions close to the subiculum was similar to that of CA1 fibers or subiculum fibers, respectively. The presubiculum sent fibers mainly to the medial EC; most densely to layers I and III. The parasubiculum sent fibers mainly to the medial EC; most densely to layer II. Fibers to the contralateral EC were detected only from the presubiculum; they originated from the superficial layers and terminated in layer III of the medial entorhinal area.