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Visual Image (left), Infrared image (right)Rattlesnakes
may shift between visual (eyes) and infrared (facial pits)
stimuli without significant loss of predatory performance
during an envenomating strike. The relative equivalency of
these proximate stimuli is correlated with the organization
of the associated neural pathways in the central nervous
system. Visual and infrared information, although gathered
by different sensory organs, converge within the optic
tectum in an orderly spatiotopical representation where
bimodal neurons respond to both stimuli. In turn, the tectum
sends efferent pathways directly to premotor (brainstem) and
indirectly to motor areas (spinal cord) where axial muscles
involved in the strike might be activated.
On the other hand, rattlesnakes do not maintain a high
level of equivalent predatory performance when switching
between chemosensory stimuli, olfactory and vomeronasal (VNO)
information. Deprived of vomeronasal input, strikes drop by
about half, and poststrike trailing is lost entirely.
Surprisingly, compensation by switching to information
delivered via an intact olfactory input does not occur,
despite the convergence of chemosensory information within
the central nervous system.
Finally, the launch of a targeted, envenomating strike
involves both these modalities, radiation reception (visual,
infrared) and chemoreception (olfactory, vomeronasal).
However, in the absence of chemosensory information (VNO),
the radiation modalities do not completely compensate nor
maintain a high level of predatory performance. Conversely,
in the absence of radiation information, the chemosensory
modalities do not completely compensate nor maintain a high
level of predatory performance. This absence of compensation
in this multimodal system is also correlated with an absence
of convergence of radiation and chemical information in the
central nervous system.
See: Kardong, K. V. and H. Berkhoudt. 1998.
Rattlesnake Hunting Behavior: Correlations Between
Plasticity of Predatory Performance and Neuroanatomy. Brain,
Behavior, Evolution.
Other
References
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