Detection of an inhibitory cortical gradient underlying peak shift in learningстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 19 сентября 2017 г.
Аннотация:Experience often does not produce veridical memory. Understanding false attribution of events constitutes
an important problem in memory research. ‘‘Peak shift’’ is a well-characterized, controllable phenomenon
in which human and animal subjects that receive reinforcement associated with one sensory
stimulus later respond maximally to another stimulus in post-training stimulus generalization tests. Peak
shift ordinarily develops in discrimination learning (reinforced CS+, unreinforced CS) and has long been
attributed to the interaction of an excitatory gradient centered on the CS+ and an inhibitory gradient centered
on the CS; the shift is away from the CS. In contrast, we have obtained peak shifts during single
tone frequency training, using stimulation of the cholinergic nucleus basalis (NB) to implant behavioral
memory into the rat. As we also recorded cortical activity, we took the opportunity to investigate the possible
existence of a neural frequency gradient that could account for behavioral peak shift. Behavioral frequency
generalization gradients (FGGs, interruption of ongoing respiration) were determined twice
before training while evoked potentials were recorded from the primary auditory cortex (A1), to obtain
a baseline gradient of ‘‘habituatory’’ neural decrement. A post-training behavioral FGG obtained 24 h
after three daily sessions of a single tone paired with NB stimulation (200 trials/day) revealed a peak shift.
The peak of the FGG was at a frequency lower than the CS while the cortical inhibitory gradient was at a
frequency higher than the CS frequency. Further analysis indicated that the frequency location and magnitude
of the gradient could account for the behavioral peak shift. These results provide a neural basis for
a systematic case of memory misattribution and may provide an animal model for the study of the neural
bases of a type of ‘‘false memory’’.