Abstract
摘要:大腦皮質(cerebral cortex)在初階訊息整合到高階認知功能都扮演重要角色。在人類及台灣獼猴,大腦皮質佔腦比超過2/3 (齧齒類則少於1/3),且均由6個互聯堆棧的皮質層所組成。過去研究發現,主要視覺區不同皮質層神經其反應特性有明顯差異—當使用不同刺激型態時,訊號輸出層神經的反應特性會隨刺激型態變化,但訊號輸入層神經的反應則無明顯變化,顯示其功能性可能有所不同。本研究計畫運用多頻道電極,在主要視覺與觸覺區同時記錄大腦不同分層之神經訊號及其電位變化,透過分析神經反應、神經共振(synchrony)和脊波引發電位變化(spike-triggered local field potential)訊號,來瞭解皮質區不同皮質層神經元群體編碼、運算及迴路運作。我們假設皮質間訊號主導(cortico-cortical)的神經元,較受視丘訊號主導(thalamo-cortical)的神經元更具可塑性,其網絡受不同刺激型態影響也較大。本計畫以台灣獼猴為模型,主要目標: (1)同時記錄主要視覺(V1)與觸覺區(S1),分析不同皮質層神經迴路是否在不同皮質區有所差異。(2)神經元在相同皮層內與不同皮層間的功能性連結,如何受不同刺激型態調控。(3)相似的視觸刺激,在不同感覺訊息處理階段是否有所差異。藉由這些研究結果我們會試圖模擬大腦皮質如何處理外界訊息,進而對大腦處理訊息原則提供寶貴線索,結果將有助於最佳化視覺與觸覺輔具。
Abstract: The cerebral cortex is essential not only for integrating sensory information but also for higher cognitive functions. In humans and macaque monkeys, the cerebral cortex occupies more than 2/3 of the brain volume (less than 1/3 in rodents), and is consisted of six distinct laminar structures that differ in cell types and functional connections. Many studies in primary visual cortex (V1) of monkeys found that neurons in different layers differed significantly in responses properties. In comparison with neurons in the input layer of V1, many neurons in the output layer responded differently when they were stimulated with different stimulus ensembles. These results indicate that V1 circuitry is highly flexible and can adapt accordingly to the change of input signals. However, the neural circuitry underlying the contextual change of individual neurons in V1 remains unclear. It is also unclear how the connectivity within the same layer or across different layers of the neocortex is modulated by different stimuli. The proposal is a continuation of the project funded last year. We plan to use the multi-electrode system to record simultaneously from multiple neurons in both primary visual cortex (V1) and primary somatosensory cortex (S1) of macaque monkeys. This multi-neuron and multi-area approaches allow us to study functional connectivity of neurons within the same cortical layer and across different layers in different sensory modalities. We hypothesize that the cortico-cortical dominated layer (i.e. layer 2/3, with abundant recurrent circuitry) may show higher degree of flexibility when encounter different stimulus conditions than the thalamo-cortical dominated layer (i.e. layer 4c). We will record broad-band signals from multiple channels simultaneously, and study how the property of individual neurons and different laminar circuitries with different stimuli. Here we propose three specific aims. Aim 1: Characterizing features of the functional connectivity within the same and across different layers in V1 and S1. This aim is essential because neurons in different cortical layers of V1 and S1 show different response properties, but the circuitry underlying these differences is still poorly understood. Aim 2: Investigating how features of the functional connectivity are modulated by different visual and somatosensory stimuli. Many V1 simple cells in the cortico-cortical dominated layer show a strong stimulus-dependent effect - their receptive fields change accordingly with different stimulus ensembles. It is possible that the recurrent excitation within the cortico-cortical dominated layer is responsible for the ample contextual effect. We will also focus on how functional connectivity within the same layer and across different layers of the cerebral cortex is modulated by different stimuli. Aim 3: Studying how response properties changes across different stages of sensory processing, and investigating the difference between V1 and S1 circuitries. Also, we are interested in whether visual stimulus along might modulate activity in S1 and vice versa, because visual and somatosensory information must be combined to from precise textile perception. Results from these projects will be employed to a multi-neuron multi-layer computational model to simulate cortical processing. These results offer invaluable insight about the general rules of information processing of the neocortex.
Keyword(s)
主要視覺皮質區
主要觸覺皮質區
神經共振
視覺與觸覺受域
脊波引發電位變化
台灣獼猴
primary visual cortex V1
primary somatosensory cortex S1
synchrony
receptive field
spike-triggered local field potential
macaque monkey