Generation of fractal patterns for probing the visual memory

Miyashita, Yasushi; Higuchi, Seiichi; Sakai, Katsuyuki; Masui, Naohiko

doi:10.1016/0168-0102(91)90121-e

Cited by 74 publications

(52 citation statements)

References 8 publications

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“…This is a task that has been demonstrated to elicit robust activation of the MTL, and therefore served as a benchmark task in evaluating the scanning and analysis methods. The stimuli were randomly generated kaleidoscope images [Miyashita et al, 1991]. For 132 trials per scan run, participants were first shown a stimulus with four square outlines superimposed on it.…”

Section: Behavioral Methodsmentioning

confidence: 99%

High‐resolution fMRI investigation of the medial temporal lobe

Kirwan¹,

Jones²,

Miller³

et al. 2006

Human Brain Mapping

121

109

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The medial temporal lobe (MTL) is critical for declarative memory formation. Several theories of MTL function propose functional distinctions between the different structures of the MTL, namely the hippocampus and the surrounding cortical areas. Furthermore, computational models and electrophysiological studies in animals suggest distinctions between the subregions of the hippocampus itself. Standard fMRI resolution is not sufficiently fine to resolve activity on the scale of hippocampal subregions. Several approaches to scanning the MTL at high resolutions have been made, however there are limitations to these approaches, namely difficulty in conducting group-level analyses. We demonstrate here techniques for scanning the MTL at high resolution and analyzing the high-resolution fMRI data at the group level. To address the issue of cross-participant alignment, we employ the ROI-LDDMM alignment technique, which is demonstrated to result in smaller alignment errors when compared with several other common normalization techniques. Finally, we demonstrate that the pattern of activation obtained in the high-resolution functional data is similar to that obtained at lower resolution, although the spatial extent is smaller and the percent signal change is greater. This difference in the pattern of activation may be due to less partial volume sampling in the high-resolution data, resulting in more accentuated regions of activation.

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Section: Behavioral Methodsmentioning

confidence: 99%

High‐resolution fMRI investigation of the medial temporal lobe

Kirwan¹,

Jones²,

Miller³

et al. 2006

Human Brain Mapping

121

109

View full text Add to dashboard Cite

show abstract

“…The stimuli consisted of computer-generated geometric patterns of kaleidoscope-like images (Miyashita et al, 1991) generated randomly for each participant. Stimuli were displayed using a native Visual C application on the Windows 2000 operating system, with the Allegro 4.0 gaming library (Hargreaves, 2003).…”

Section: Methodsmentioning

confidence: 99%

Functional Magnetic Resonance Imaging Activity during the Gradual Acquisition and Expression of Paired-Associate Memory

Law

Flanery

Wirth

et al. 2005

Journal of Neuroscience

123

134

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Recent neurophysiological findings from the monkey hippocampus showed dramatic changes in the firing rate of individual hippocampal cells as a function of learning new associations. To extend these findings to humans, we used blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to examine the patterns of brain activity during learning of an analogous associative task. We observed bilateral, monotonic increases in activity during learning not only in the hippocampus but also in the parahippocampal and right perirhinal cortices. In addition, activity related to simple novelty signals was observed throughout the medial temporal lobe (MTL) memory system and in several frontal regions. A contrasting pattern was observed in a frontoparietal network in which a high level of activity was sustained until the association was well learned, at which point the activity decreased to baseline. Thus, we found that associative learning in humans is accompanied by striking increases in BOLD fMRI activity throughout the MTL as well as in the cingulate cortex and frontal lobe, consistent with neurophysiological findings in the monkey hippocampus. The finding that both the hippocampus and surrounding MTL cortex exhibited similar associative learning and novelty signals argues strongly against the view that there is a clear division of labor in the MTL in which the hippocampus is essential for forming associations and the cortex is involved in novelty detection. A second experiment addressed a striking aspect of the data from the first experiment by demonstrating a substantial effect of baseline task difficulty on MTL activity capable of rendering mnemonic activity as either "positive" or "negative."

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“…3A). We generated the patterns according to the algorithm described previously (16) and arranged them into 12 pairs. In the task, following a fixation stimulus, a cue stimulus was presented in the center of the video monitor for 0.5 s. After a delay period, the paired associate of the cue stimulus and one stimulus from a different pair were shown.…”

Section: Methodsmentioning

confidence: 99%

Formation of mnemonic neuronal responses to visual paired associates in inferotemporal cortex is impaired by perirhinal and entorhinal lesions.

Higuchi

Miyashita

1996

Proc. Natl. Acad. Sci. U.S.A.

251

178

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Functional roles of the cortical backward signal in long-term memory formation were studied in monkeys performing a visual pair-association task Before the monkeys learned the task, the anterior commissure was transected, disconnecting the anterior temporal cortex of each hemisphere. After training with 12 pairs of pictures, single units were recorded from the inferotemporal cortex of the monkeys as the control. By injecting a grid of ibotenic acid, we unilaterally lesioned the entorhinal and perirhinal cortex, which provides massive direct and indirect backward projections ipsilaterally to the inferotemporal cortex. After the lesion, the monkeys fixated the cue stimulus normally, relearned the preoperatively learned set (set A), and learned a new set (set B) of paired associates. Then, single units were recorded from the same area as for the prelesion control. We found that (i) in spite of the lesion, the sampled neurons responded strongly and selectively to both the set A and set B patterns and (ii) the paired associates elicited significantly correlated responses in the control neurons before the lesion but not in the cells tested after the lesion, either for set A or set B stimuli. We conclude that the ability of inferotemporal neurons to represent association between picture pairs was lost after the lesion of entorhinal and perirhinal cortex, most likely through disruption of backward neural signals to the inferotemporal neurons, while the ability of the neurons to respond to a particular visual stimulus was left intact.

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Generation of fractal patterns for probing the visual memory

Cited by 74 publications

References 8 publications

High‐resolution fMRI investigation of the medial temporal lobe

High‐resolution fMRI investigation of the medial temporal lobe

Functional Magnetic Resonance Imaging Activity during the Gradual Acquisition and Expression of Paired-Associate Memory

Formation of mnemonic neuronal responses to visual paired associates in inferotemporal cortex is impaired by perirhinal and entorhinal lesions.

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