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Yoshio Sakurai

Publications and source records attributed to Yoshio Sakurai.

7 recordsLinked to original sources
PubMed2004

Behavioral studies of auditory-visual spatial recognition and integration in rats.

Rodents are useful animal models in the study of the molecular and cellular mechanisms underlying various neural functions. For studying behavioral properties associated with multisensory functions in rats, we measured the speed and accuracy of target detection by the reaction-time procedure. In the first experiment, we utilized simple two-alternative-choice tasks, in which spatial cues are visual or auditory modalities, and conducted a cross-modal transfer test in order to determine whether rats recognize amodal spatial information. Rats showed successful performance in the cross-modal transfer test and the speed to respond to sensory stimuli was constant under a rule-consistent condition despite the change in cue modality. In the second experiment, we developed audiovisual two-alternative-choice tasks, in which both auditory and visual stimuli were simultaneously presented but one of the two modalities was task-relevant, in order to determine whether the response to the sensory stimulation of one modality is enhanced by the stimulation of a different modality. If bimodal stimuli were spatially coincident, the speed for detecting the relevant stimulus was shortened and the extent of the effect was comparable to those in past studies of humans and other mammals. These results indicate the cross-modal spatial abilities of rats and our present paradigms may provide useful behavioral tasks for studying the neural bases of multisensory processing and integration in rats.

Acoustic Stimulation↗
PubMed2004

Stimulus duration in working memory is represented by neuronal activity in the monkey prefrontal cortex.

Humans are capable of memorizing several attributes of a presented stimulus as well as its duration of presentation. However, the neuronal representation of stimulus duration in memory remains unknown. This study investigated activities of single neurons in the prefrontal cortex of monkeys while they were performing a behavioral task in which working memory for stimulus duration was needed. Here we describe specific neurons whose discharge rates reflect encoding or retention of the duration of the presentation of stimuli to be remembered. We also describe other specific neurons whose activities reflect encoding or retention of fixed duration, similar but unrelated to the stimulus duration presented in each trial. Some of these specific neurons showed the same duration-related discharges even while the monkeys were performing a different task, in which working memory for stimulus duration was no longer needed. From these results, we suggest that neurons in the prefrontal cortex play roles in encoding and retention of temporal information in working memory and that some of those neurons are dedicated to representation of temporal information attributed to stimuli even when the temporal information is unnecessary for correct performance.

Action Potentials↗
PubMed2003

Simultaneous determination of endocannabinoids (arachidonylethanolamide and 2-arachidonylglycerol) and isoprostane (8-epiprostaglandin F2alpha) by gas chromatography-mass spectrometry-selected ion monitoring for medical samples.

This article describes the overall procedure for the simultaneous determination of endocannabinoids (arachidonylethanolamide and 2-arachidonyglycerol) and isoprostane by gas chromatography-mass spectrometry in the selected-ion monitoring SIM mode (GC-MS-SIM) for medical samples. It also describes the general points of this method which a scientist who wants to assay a new, unidentified prostanoids and related compounds in medical samples would need to be clarified. The similar structures of prostaglandins, thromboxane, their metabolites, isoprostane, and arachidonyl compounds, allow them to be assayed after the simultaneous preparation of a single sample. The dimethyl isopropylsilyl ether forms of derivatized compounds are suitable for multiple GC-MS-SIM assay because of their molecular stability, and because they produce positive, strong, and large fragments on MS.

Arachidonic Acids↗
PubMed2003

A new approach to spike sorting for multi-neuronal activities recorded with a tetrode--how ICA can be practical.

Multi-neuronal recording with a tetrode is a powerful technique to reveal neuronal interactions in local circuits. However, it is difficult to detect precise spike timings among closely neighboring neurons because the spike waveforms of individual neurons overlap on the electrode when more than two neurons fire simultaneously. In addition, the spike waveforms of single neurons, especially in the presence of complex spikes, are often non-stationary. These problems limit the ability of ordinary spike sorting to sort multi-neuronal activities recorded using tetrodes into their single-neuron components. Though sorting with independent component analysis (ICA) can solve these problems, it has one serious limitation that the number of separated neurons must be less than the number of electrodes. Using a combination of ICA and the efficiency of ordinary spike sorting technique (k-means clustering), we developed an automatic procedure to solve the spike-overlapping and the non-stationarity problems with no limitation on the number of separated neurons. The results for the procedure applied to real multi-neuronal data demonstrated that some outliers which may be assigned to distinct clusters if ordinary spike-sorting methods were used can be identified as overlapping spikes, and that there are functional connections between a putative pyramidal neuron and its putative dendrite. These findings suggest that the combination of ICA and k-means clustering can provide insights into the precise nature of functional circuits among neurons, i.e. cell assemblies.

Action Potentials↗
PubMed2002

Automatic sorting for multi-neuronal activity recorded with tetrodes in the presence of overlapping spikes.

Multi-neuronal recording is a powerful electrophysiological technique that has revealed much of what is known about the neuronal interactions in the brain. However, it is difficult to detect precise spike timings, especially synchronized simultaneous firings, among closely neighboring neurons recorded by one common electrode because spike waveforms overlap on the electrode when two or more neurons fire simultaneously. In addition, the non-Gaussian variability (nonstationarity) of spike waveforms, typically seen in the presence of so-called complex spikes, limits the ability to sort multi-neuronal activities into their single-neuron components. Because of these problems, the ordinary spike-sorting techniques often give inaccurate results. Our previous study has shown that independent component analysis (ICA) can solve these problems and separate single-neuron components from multi-neuronal recordings. The ICA has, however, one serious limitation that the number of separated neurons must be less than the number of electrodes. The present study combines the ICA and the efficiency of the ordinary spike-sorting technique (k-means clustering) to solve the spike-overlapping and the nonstationarity problems with no limitation on the number of single neurons to be separated. First, multi-neuronal activities are sorted into an overly large number of clusters by k-means clustering. Second, the sorted clusters are decomposed by ICA. Third, the decomposed clusters are progressively aggregated into a minimal set of putative single neurons based on similarities of basis vectors estimated by ICA. We applied the present procedure to multi-neuronal waveforms recorded with tetrodes composed of four microwires in the prefrontal cortex of awake behaving monkeys. The results demonstrate that there are functional connections among neighboring pyramidal neurons, some of which fire in a precise simultaneous manner and that precisely time-locked monosynaptic connections are working between neighboring pyramidal neurons and interneurons. Detection of these phenomena suggests that the present procedure can sort multi-neuronal activities, which include overlapping spikes and realistic non-Gaussian variability of spike waveforms, into their single-neuron components. We processed several types of synthesized data sets in this procedure and confirmed that the procedure was highly reliable and stable. The present method provides insights into the local circuit bases of excitatory and inhibitory interactions among neighboring neurons.

Action Potentials↗
PubMed2002

Task-dependent and cell-type-specific Fos enhancement in rat sensory cortices during audio-visual discrimination.

Attention modulates neural activities in sensory cortices. Because cortical neurons are composed of many types of neurons, the activities of these different types of cells can exhibit different modifications depending on whether an animal pays attention to a particular sensory stimulus or not. In the present study, we examined which types of cortical neurons change their activities in rats during one of two types of audio-visual discrimination (AVD) tasks by using Fos immunohistochemistry. In the tasks, both auditory and visual stimuli were simultaneously presented but only one of the two modalities was task-relevant. Once the rats had learned one of the AVD tasks, presenting only relevant sensory stimuli was sufficient for them to perform the task correctly. These results suggest that the rats indeed attended to the relevant stimuli during the performance of the tasks. We found that Fos expression in the primary auditory and visual cortices was enhanced in a task-dependent manner during the performance of the AVD tasks. The enhancement of Fos expression depended on the behavioural significance of the stimulus in the tasks. Moreover, using double immunohistochemistry of Fos and a cell type-specific marker protein (phosphate-activated glutaminase, nonphosphorylated neurofilament protein, parvalbumin, calretinin or somatostatin), the task-dependent Fos expression was observed preferentially in excitatory neurons but not in inhibitory interneurons. These results suggest that modulation in cortical excitatory neurons might have critical roles in selecting and processing behaviourally relevant sensory stimuli.

Animals↗