Biology Reference
In-Depth Information
Chapter 9
C
ELLULAR
C
OGNITION
:
A
F
OCUS ON
LT P
AND
LT D
IN THE
L
ATERAL
N
UCLEUS OF THE
A
MYGDALA
Doris Albrecht and Oliver von Bohlen und Halbach
A
BSTRACT
Synaptic plasticity is a fundamental process underlying learning and memory formation.
Long-term potentiation (LTP) and long-term depression (LTD) are the predominant
experimental models used for studying the mechanisms of synaptic plasticity. This
chapter focuses on signal molecules and signaling cascades involved in pre- and
postsynaptic mechanisms that contribute to the induction of LTP and LTD in a key
structure of the limbic system, the lateral nucleus of the amygdala (LA). The amygdala is
a component of the limbic system that plays a central role in emotional behavior
predominantly in fear conditioning. Moreover, the amygdala is involved in certain
psychopathologies, like epilepsy or major depression. The amygdala is a complex
structure, composed of different brain nuclei, whereby the LA seems to play an essential
role for the amygdala, since the LA represents the main input station of the amygdala.
Since a large body of literature highlights the role of the amygdala in fear learning, we
will therefore focus primarily on differences and similarities in long-term transmission
changes recorded in coronal and horizontal brain slices of mice and rats. Topics include
the four cardinal features of synaptic plasticity in the LA (cooperativity, associativity,
persistence, and input-specificity). Further topics include the modulatory actions of
various transmitter systems on amygdaloid plasticity, evidences for upregulated
postsynaptic mechanisms in LTP, and the role of gene expression regulation in the
maintenance of LTP. Moreover, we will shed light onto the paradigms used to induce
synaptic plasticity, since, depending on the used stimulation protocols, multiple, different
forms of LTP and LTD can be induced in the LA. Furthermore, it is known that the
efficiency of transmission across synapses can be potentiated or depressed in response to
a prior history of stimulation. We will present data that support the finding that this
phenomenon, called metaplasticity, is not restricted to the cortex and hippocampus, but
can also be observed at the level of the amygdala. Last, but not least, we will also briefly
discuss the impact of age and gender on LTP and LTD within the LA.
