Lectures for Animal Behavior

Animal Behavior - Biology 420/543

Bowling Green State University, Fall 2008

Sensory Processing

<Receptive Field>: In sensory systems, the specific region of a sensory surface (e.g., specific area on the retina) that when stimulated causes a change in activity of a neuron

Neural design features

Coincidence Detection:

Spatial Summation: if a neuron receives inputs from multiple sources it will respond best if the input from these sources matches in time. Activity in either presynaptic neuron alone is not sufficient to produce and action potential in the postsynaptic neuron, but an action potential is produced if signals arrive at the same time in both presynaptic inputs.

Contrast Enhancement:

Lateral Inhibition: Multiple units with similar characteristics are wired to inhibit each other's activity. The unit that fires first/strongest will prevent all others from firing. (e.g., Discrimination of left vs. right in auditory signals using a pair of Omega neurons in crickets).

Measure Time-Delay between two inputs

Delay Lines: Action potentials (AP) travel along axons at a defined speed. They thus take longer to arrive at the target the further the AP needs to travel. Multiple neurons with similar characteristics are layed out in a longitudinal array. They receive input from two sources one fed in from one side of the array, the other from the other side. Acting as coincidence detectors they respond best when the signals on both inputs match. Each member of the array is most sensitive to a particular time difference. (e.g., Spatial localization of auditory signals in the laminaro nucleus of Owls).

Acoustic processing

When localizing a sound source, systems for the discrimination of left vs. right are often based on two sub-systems. These are often mirror-images of each other and located to the left and the right of the midline (i.e., Omega neurons in crickets). They are tightly coupled through lateral inhibition, where activation of one side automatically shuts off its contralateral (i.e., opposite side) opponent. Such a design is uniquely able to allow resolution of extremely small time differences in when a sound signal arrives at the ear facing the source than in the one facing away.

Reading Assignment

Chapter 7: The Nervous System and Behavior
Suggested reading: Oliver Sacks (1998): "The Man Who Mistook His Wife For A Hat: And Other Clinical Tales" Touchstone Books, ISBN: 0684853949, 256 pages

WikiBooks

Proximate Mechanisms in Behavior

Food for Thought

What has made humans so immensely successful?

last modified: 11/17/04