Behavior and Neurology of Lizards 
N. Greenberg and P. D. MacLean, eds. 
NIMH, 1977. 
Behavioral Responses to the Electrical Stimulation of the 
Brain in the Green Iguana. 
Hansjiirgen Distel* 
Max-Planck-Institut fiir Psychiatric 
In order to identify behavioral patterns 
and related brain areas amenable to more 
specific neurobehavioral investigations, the 
brains of 21 large green iguanas (Iguana 
iguana L.), 16 males and 5 females from 
Colombia, were explored with stimulating 
electrodes (Distel, 1976, in press). 
The responses elicited by stimulation at 518 
sites are presented in figures 1-5, The 
symbols in the figures indicate behavioral 
sequences elicited for a given range of 
stimulus intensities, rather than single be- 
havioral units. Generally, the filled symbols 
indicate the occurrence of locomotion, where- 
as the open ones indicate the absence of 
locomotion. Two symbols were combined 
when responses changed and more than one 
sequence of responses occurred, e.g., an open 
diamond on top of a filled triangle means a 
change from a dewlap display to an escape 
response. Finally, circles around symbols 
indicate similar responses confirmed in dif- 
ferent animals at equivalent stimulation sites. 
Tongue-flicking responses were elicited 
fairly nonspecifically (for example after ces- 
sation of the stimulus). However, all stimu- 
lated areas which were part of the afferent 
olfactory system, such as the tuberculum 
olfactorium or the nucleus sphericus, yielded 
strong tongue-flicking responses, as did a 
region extending from the nucleus accumhens 
to the hypothalamus, and a more isolated area 
next to the oculomotor nucletis. Although 
tongue-flicking as a typical exploratory be- 
havior is susceptible to generally arousing 
stimuli, its dependence on the olfactory struc- 
tures is suggested by these results. 
Eye-closing was generally preceded by 
Present address: Institut Mediz. Psychologie, 
Pettenkoferstr. 12,8000 Miinchen 2, West Germany 
retreat and escape responses and was, there- 
fore, regarded as a pre-escape behavior. Eye 
closing and escape responses were elicited at 
stimulation sites throughout the brain, but 
eye-closing always occurred first and by 
lower stimulating intensities. This relation- 
ship and the simplicity of the response make 
eye-closing especially appropriate for further 
experimental study of avoidance behavior in 
the green iguana. 
Violent flight responses developed abruptly 
and were preceded and followed by very little 
other behavior. They were elicited by stimu- 
lation at sites located in the deep tectal 
layers, throughout the tegmentum, and in the 
lateral medulla oblongata. 
Dewlap (throat fan) displays were elicited 
by stimulation at many sites. They regu- 
larly preceded the defensive displays which 
were with few exceptions elicited only from 
sites in the hypothalamus. Head-nodding dis- 
plays were seldom reliably elicited during 
stimulation and then only after long laten- 
cies. They occurred, however, immediately 
after stimulation ceased. Typically, when an 
aggressive animal is about to escape because 
of brain stimulation, and the stimulus is 
turned off at this moment, head-nodding dis- 
play will occur. A functional relationship of 
the head-nodding display to displacement be- 
havior is strongly suggested by these experi- 
ments, 
REFERENCES 
Distel, H. 1976. Behavior and electrical brain stimu- 
lation in the green iguana, Iguana iguana L. I. 
Schematic brain atlas and stimulation device. 
Brain, Behav. Evol. 13:421-450. 
Distel, H. Behavior and electrical brain stimulation 
in the green iguana, Iguana iguana L. II. Stimu- 
lation effects, Exp. Brain Res. (In press) 
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