Gain control is a salient feature of information processing throughout
the visual system. Heeger (1991, 1992) described a mechanism that could
underpin gain control in primary visual cortex (V1). According to this model,
a neuron's response is normalized by dividing its output by the sum of
a population of neurons, which are selective for orientations covering a
broad range. Gain control in this scheme is manifested as a change in the
semisaturation constant (contrast gain) of a V1 neuron. Here we examine how
flanking and annular gratings of the same or orthogonal orientation to that
preferred by a neuron presented beyond the receptive field modulate
gain in V1 neurons in anesthetized marmosets (Callithrix
jacchus). To characterize how gain was modulated by surround
stimuli, the Michaelis–Menten equation was fitted to response
versus contrast functions obtained under each stimulus
condition. The modulation of gain by surround stimuli was modelled best
as a divisive reduction in response gain. Response gain varied with the
orientation of surround stimuli, but was reduced most when the
orientation of a large annular grating beyond the classical receptive
field matched the preferred orientation of neurons. The strength of
surround suppression did not vary significantly with retinal
eccentricity or laminar distribution. In the marmoset, as in macaques
(Angelucci et al., 2002a, b), gain control over the
sort of distances reported here (up to 10 deg) may be mediated by feedback
from extrastriate areas.
增益控制是整个视觉系统信息处理的一个突出特点。
增益控制是整个视觉系统信息处理的显著特征。Heeger(1991 年、1992 年)描述了一种机制,它可能是初级视觉皮层(V1)增益控制的基础。
增益控制的机制。根据这一模型
神经元的响应是通过将其输出除以一组神经元的总和来归一化的。
神经元群的总和进行归一化。
的神经元群。这种方案中的增益控制表现为半饱和常数(对比度增益)的变化。
V1 神经元的半饱和常数(对比度增益)的变化。在此,我们研究了
与神经元偏好的方向相同或正交的侧翼光栅和环形光栅是如何控制的?
神经元偏好的同方向或正交方向光栅如何调节
麻醉狨猴(Callithrix
jacchus)V1神经元的增益。为了描述增益如何受周围
刺激对增益的调节特性,用迈克尔斯-门顿方程拟合了在每种刺激下获得的反应
与对比度函数进行拟合。
条件下获得的反应与对比度函数进行了拟合。环绕刺激对增益的调制效果最好
为反应增益的分化降低。反应增益随
反应增益随环绕刺激物的方向而变化,但当环绕刺激物的方向超出感知范围时,反应增益的降低幅度最大。
当经典感受野之外的大环形光栅的方向与神经元偏好的方向一致时,反应增益降低得最多。
与神经元偏好的方向一致时,反应增益的降低幅度最大。环绕抑制的强度
环绕抑制的强度与视网膜
偏心率或层状分布的差异不大。在狨猴和猕猴中(Angelucci et al.
(Angelucci等人,2002a, b)一样,在狨猴中,获得控制的距离
在狨猴身上,与猕猴一样(Angelucci et al.
的反馈。