Stimulus Competition by Inhibitory Interference

• Published in: Neural computation Vol. 17; no. 11; pp. 2421 - 2453
• Main Author: Tiesinga, Paul H. E.
• Format: Journal Article
• Language: English
• Published: One Rogers Street, Cambridge, MA 02142-1209, USA MIT Press 01.11.2005; MIT Press Journals, The
• Subjects: Animals; Applied sciences; Artificial intelligence; Attention - physiology; Biological and medical sciences; Cognition & reasoning; Computer science; control theory; systems; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General aspects. Models. Methods; Humans; Miscellaneous; Models, Neurological; Nerve Net - cytology; Nerve Net - physiology; Neural Inhibition - physiology; Neurons; Neurons - physiology; Photic Stimulation - methods; Reaction Time - physiology; Synapses - physiology; Time Factors; Vertebrates: nervous system and sense organs; Visual Cortex - cytology; Visual Fields - physiology; Visual Pathways; Competition; Neural computation; Receptive field; Stimulus; Neuronal discharge; Inhibitor interference; Firing rate; Neural network; Local network; Interneuron; Eye; Arrival time; Experimental result; Information processing; Delay time; Excitation; Inhibition; Gain; Biased estimation
• ISSN: 0899-7667; 1530-888X
• DOI: 10.1162/0899766054796905

When two stimuli are present in the receptive field of a V4 neuron, the firing rate response is between the weakest and strongest response elicited by each of the stimuli when presented alone (Reynolds, Chelazzi, & Desimone, 1999). When attention is directed toward the stimulus eliciting the strongest response (the preferred stimulus), the response to the pair is increased, whereas the response decreases when attention is directed to the other stimulus (the poor stimulus). When attention is directed to either of the two stimuli presented alone, the firing rate remains the same or increases slightly, but the coherence between the neuron's spike train and the local field potential can increase (Fries, Reynolds, Rorie, & Desimone, 2001). These experimental results were reproduced in a model of a V4 neuron under the assumption that attention modulates the activity of local interneuron networks. The V4 model neuron received stimulus-specific excitation from V2 and synchronous inhibitory inputs from two local interneuron networks in V4. Each interneuron network was driven by stimulus-specific excitatory inputs from V2 and was modulated by the activity of the frontal eye fields. Stimulus competition was present because of a delay in arrival time of synchronous volleys from each interneuron network. For small delays, the firing rate was close to the rate elicited by the preferred stimulus alone, whereas for larger delays, it approached the firing rate of the poor stimulus. When either stimulus was presented alone, the neuron's response was not altered by the change in delay, but could change due to modulation of the degree of synchrony of the corresponding interneuron network. The model suggests that top-down attention biases the competition between V2 columns for control of V4 neurons primarily by changing the relative timing of inhibition, whereas changes in the degree of synchrony of interneuron networks modulate the response to a single stimulus. The new mechanism proposed here for attentional modulation of firing rate, , is likely to have more general applicability to cortical information processing.