Frequency response characteristics of lateral geniculate nucleus and primary visual cortex
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1
Istanbul University, Türkiye
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2
Bogazici University, Türkiye
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3
Uskudar University, Türkiye
Studies measuring fMRI BOLD signal have shown that responses of the primary visual area (V1) do not change uniformly or monotonously with the flickering frequencies. Besides, there are evidences that changes in frequency characteristics begin to emerge at the level of the lateral geniculate nucleus (LGN). We therefore set out to investigate BOLD response of the human V1 and LGN with flickering light at systematically varying frequencies between 6 and 46 Hz. The blood oxygenation level-dependent (BOLD) responses to 6, 8, 10, 12, 14, 18, 22, 26, 30, 34, 38, 42 and 46 Hz flicker visual stimulations in the primary visual cortex and lateral geniculate nuclei were investigated in 35 healthy volunteers. fMRI analysis was performed with SPM5 software. Single subject multi-session fixed-effects analysis results of each subject were thresholded at a significance level of p < .05 (uncorrected) and after masking with template LGN and V1 masks, they were binarized. Active LGN and V1 masks specific to subject were used to extract parameter estimates ('beta' images) of each frequency. Normalized average 'beta'-value changes with stimulation frequency for LGN and V1 were calculated and compared. A highly significant correlation between LGN and V1 responses was observed across the stimulation frequencies (p < .0001), reflecting a strong match of the local maxima probably due to the preferred thalamo-cortical interaction around specific frequencies. However, BOLD amplitudes of V1 showed a stronger decline with increasing frequencies, while they were relatively spared in the LGN. This suggests that the thalamus relays a steady visual input at a high frequency with limited output to the cortex. Funding: This study is supported by TUBITAK project #108S101.
Keywords:
Brain Signals,
fMRI
Conference:
XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011.
Presentation Type:
Poster Presentation
Topic:
Poster Sessions: Modeling and Analysis of Brain Signals
Citation:
Demiralp
T,
Bayram
A,
Karahan
E,
Bilgiç
B,
Tarhan
N and
Ademoğlu
A
(2011). Frequency response characteristics of lateral geniculate nucleus and primary visual cortex.
Conference Abstract:
XI International Conference on Cognitive Neuroscience (ICON XI).
doi: 10.3389/conf.fnhum.2011.207.00080
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Received:
16 Nov 2011;
Published Online:
25 Nov 2011.
*
Correspondence:
Prof. Tamer Demiralp, Istanbul University, Istanbul, Türkiye, demiralp@istanbul.edu.tr