ABSTRACT
Since the 1970s, human subjects that have undergone corpus callosotomy have provided important insights into neural mechanisms of perception, memory, and cognition. The ability to test the function of each hemisphere independently of the other offers unique advantages for investigating systems that are thought to underlie cognition. However, such approaches have been limited to mammals. Here we describe comparable experiments on an insect brain to demonstrate learning-associated changes within one brain hemisphere. After training one half of their bisected brains, cockroaches learn to extend the antenna supplying that brain hemisphere towards an illuminated diode after this has been paired with an odor stimulus. The antenna supplying the naïve hemisphere shows no response. Cockroaches retain this ability for up to 24 h, during which, shortly after training, the mushroom body of the trained hemisphere alone undergoes specific post-translational alterations of microglomerular synaptic complexes in its calyces.
Subject(s)
Behavior, Animal/physiology , Brain/physiology , Functional Laterality/physiology , Learning/physiology , Neuronal Plasticity/physiology , Animals , Blotting, Western , Brain/anatomy & histology , Conditioning, Classical/physiology , Electrophoresis, Polyacrylamide Gel , Immunohistochemistry , Neural Pathways/anatomy & histology , Neural Pathways/physiology , PeriplanetaABSTRACT
A unique behavioral paradigm has been developed for Periplaneta americana that assesses the timing and success of memory consolidation leading to long-term memory of visual-olfactory associations. The brains of trained and control animals, removed at the critical consolidation period, were screened by two-directional suppression subtractive hybridization. Screens identified neurobiologically relevant as well as novel genes that are differentially expressed at the consolidation phase of memory. The differential expression of six transcripts was confirmed with real-time RT-PCR experiments. There are mitochondrial DNA encoded transcripts among the up-regulated ones (COX, ATPase6). One of the confirmed down-regulated transcripts is RNA polymerase II largest subunit. The mitochondrial genes are of particular interest because mitochondria represent autonomous DNA at synapses. These transcripts will be used as one of several tools in the identification of neuronal circuits, such as in the mushroom bodies, that are implicated in memory consolidation.
