Selective potentiation of proximal processes: neurobiological mechanisms for spread of activation.
BACKGROUND: Signal detection by one sense selectively activates other relevant systems. For example, when an auditory stimulus comes from a specific location, visual sensitivity, tactile sensitivity, and motor readiness increase for stimuli or actions in that direction. This observed phenomenon provides an apparent sensory-sensory and sensory-motor coordination with evolutionary adaptive advantages. Anatomically, many of the relevant cortical sites are adjacent to each other. MATERIAL/METHODS: The spread of excitation from an active processing site in the cortex to nearby functions can be seen in brain scans. Cognitive and affective functions also selectively activate each other and are activated by focal sensory stimulation based on cortical proximity. These behavioral interactions seem to offer no selective adaptability but still call for a model of possible mediation. The objective of the current paper is to consider evidence for competing mechanisms for the flow of cortical activation that are characterized by being neurobiologically feasible, showing preferential activation over short distances, and having empirical support. RESULTS: These three criteria are met by blood flow, heat flow, nearest networks, electromagnetism, and inhibition. CONCLUSIONS: It is suggested that several of these mechanisms work independently or synergetically to produce the known interactions among attention, affect, cognition, and behavior. An understanding of these processes and the functional cerebral space in which they operate can suggest practical applications for the manipulation of behavior.