The influence of hippocampus on habituation of the HSR task.
Roberta Wiediger, Fran McSweeney & Jay Wright
Psychology Department - Washington State University
hippocampus is one of the
most important structures in the
mammalian brain linked to learning
and memory storage.
It has the ability to pass information
from one neuron to another, to
reconfigure and consolidate
information thus exhibiting synaptic
plasticity.
Habituation
has been defined as a
decrease in responsiveness to
repeated presentation of a stimulus
(Groves & Thompson, 1970).
It is the simplest for of learning
(Harris, 1943).
The waning of a reflexive response
to repeated stimulation (Staddon,
2001).
of habituation
McSweeney and Murphy (2000)
14 characteristics
E.g. Spontaneous recovery – the
recovery of a habituated stimulus
when that stimulus is not
presented for a period of time.
Spontaneous recovery of the
HSR was predicted for the
standard habituation group after
24hISI but NOT for the tone
habituation group.
– 32 male SpragueDawley rats
Apparatus – wood pedestal
Tone – 74dB
Air stimulus applied to the ear
10
Spontaneous recovery of
the HSR was expected to occur in
the hippocampectomized group
but NOT for the neocortex group.
Hippocampectomy
control
3.
It was anticipated that the
pattern of responding for the
tone habituation group would be
similar to the neocortex tone
group.
Behavioral Testing
HSR
task
5-min adaptation period
24 trial – 15s stimulus
presentation (air)
ITI of 15s
IBM compatible computer
signaled the intervals
Green – 15s of air
presentation
Red – 15s of ITI
Association
Tone
session
Same procedure as standard
habituation session
But
A tone was introduced 1s
preceding air presentation
The Present Study
The
No Hip Tone Session 1
No Hip Tone Session 2
Tone Cortex Session 1
Tone Cortex Session 2
8
2.
Surgeries
Characteristic
purpose of this experiment was
to determine the role of the
hippocampus during habituation of
the HSR task during a classical
conditioning paradigm (introduction
of a tone), by using
hippocampectomized rats.
1.
Subjects
Neocortex
Tone
Hippocampectomy VS Cortex Control
Mean # of HSR
The
Predictions
Method
6
4
2
0
0
2
4
6
8
3 Trial Blocks
Results
No hip session 1 = Mean 9.1 HSR
session 2 = Mean 7.8 HSR
HSR VS TONE
Neocor session 1 = Mean 8.3 HSR
10
session 2 = Mean 4.5 HSR
HSR Session 1
HSR Session 2
Tone Session 1
Tone Session 2
8
Mean # of HSR
Introduction
Discussion
6
These
data suggest that the tone is
an important component for the HSR
task to become associative
4
2
This
0
0
2
4
6
8
implies that the hippocampus is
indeed important for associative
learning to take place.
3 trial blocks
However,
Groups
4
groups of rats (8 per group)
All were tested over 2
habituation sessions with a 24h
ITI.
Group 1 – standard habituation
Group 2 – tone habituation
Group 3 – hippocampectomized
tone
Group 4 – neocortex control tone
the hippocampus is not
important for the habituation of a
non-associative task
HSR session 1 = Mean 6.3 HSR
session 2 = Mean 5.2 HSR
Tone session 1 = Mean 6.6 HSR
session 2 = Mean 2.8 HSR
References
P. M., & Thompson, R. F. (1970). Habituation: A dual-process theory. Psychological
Review, 77, 419-450.
Groves,
J.D., (1943). Habituation response decrement in the intact organism. Psychological Bulletin,
40, 385-422.
Harris,
Murphy,
E. S., McSweeney, F. K., & Kowal, B. P. (2003). Within-session decrease in operant
responding as a function of pre-session feedings. The Psychological Record, 53, 313-326.
Staddon,
J. E. R., (2001). The new behaviorism. Philadelphia, PA: Taylor & Francis.