Biomedical subjects

Madoka Matsumoto

Publications and source records attributed to Madoka Matsumoto.

4 recordsLinked to original sources

PubMed2006

Effects of novelty on activity of lateral and medial prefrontal neurons.

Detection of novel events is crucial for adapting to changing environments. The prefrontal cortex has been thought to be one of the areas involved in orienting attention to novel events. Here, we examined the effects of two components of novelty: context novelty, which purely happens when a familiar event occurs in an unpredicted situation or time and feature novelty, which happens by itself when an unfamiliar stimulus appears against the expectation of familiar ones. We trained monkeys on a task that included both novelty components and recorded the activity of neurons in the lateral and medial divisions of the prefrontal cortex. The responses of a substantial number of cells in both the lateral and medial divisions were enhanced when a familiar visual stimulus was presented in an unpredicted context. By contrast, enhancement of responses by the unfamiliarity of visual stimuli was observed mainly in cells in the lateral prefrontal cortex. These results suggest that the lateral and medial divisions of the prefrontal cortex are differentially involved in the control of attention triggered by novel sensory events.

Action Potentials↗

PubMed2006

Goal-based action selection and utility-based action bias.

According to artificial intelligence studies, goal-based and utility-based agents can select an action to attain a desired outcome. The goal-based agent sets a specific goal regardless of its utility at first, and selects the action that leads to that goal (goal-based action selection). The utility-based agent compares the utilities of different possible outcomes, and selects the action that causes the outcome with the highest utility (utility-based action bias). The medial prefrontal cortex is involved in implementing the goal-based action selection and the striatum is involved in implementing the utility-based action bias. Goal-based action selection may be temporarily dominant over the utility-based action bias in a new environment, whereas the utility-based action bias becomes dominant after acquisition of action utilities in the environment. This transition of dominance between the two decision systems may be enhanced by a reference-point shift based on the goal-setting process during goal-based action selection.

Animals↗

PubMed2006

Representation of the spatial relationship among object parts by neurons in macaque inferotemporal cortex.

We investigated object representation in area TE, the anterior part of monkey inferotemporal (IT) cortex, with a combination of optical and extracellular recordings in anesthetized monkeys. We found neurons that respond to visual stimuli composed of naturally distinguishable parts. These neurons were sensitive to a particular spatial arrangement of parts but less sensitive to differences in local features within individual parts. Thus these neurons were activated when arbitrary local features were arranged in a particular spatial configuration, suggesting that they may be responsible for representing the spatial configuration of object images. Previously it has been reported that many neurons in area TE respond to visual features less complex than natural objects, but it has remained unclear whether these features are related to local features of object images or to more global features. These results indicate that TE neurons represent not only local features but also global features such as the spatial relationship among object parts.

Anesthesia↗

PubMed2004

Localization of activity-dependent changes in blood volume to submillimeter-scale functional domains in cat visual cortex.

We have examined whether blood volume changes induced by neural activation are controlled precisely enough for us to visualize the submillimeter-scale functional structure in anesthetized and awake cat visual cortex. To activate the submillimeter-scale functional structures such as iso-orientation domains in the cortex, visual stimuli (gratings) were presented to the cats. Two methods were used to examine the spatial precision of blood volume changes including changes in total hemoglobin content and changes in plasma volume: (i) intrinsic signal imaging at the wavelength of hemoglobin's isosbestic point (569 nm) and (ii) imaging of absorption changes of an intravenously injected dye. Both measurements showed that the visual stimuli elicited stimulus-nonspecific and stimulus-specific blood volume changes in the cortex. The former was not spatially localized, while the latter was confined to iso-orientation domains. From the measurement of spatial separation of the iso-orientation domains, we estimated the spatial resolution of stimulus-specific blood volume changes to be as high as 0.6 mm. The changes in stimulus-nonspecific and -specific blood volume were not linearly correlated. These results suggest the existence of fine blood volume control mechanisms in the capillary bed in addition to global control mechanisms in arteries.

Anesthesia↗