Abstract
Repeated stimulus causes a specific suppression of neuronal responses, which is so-called as Stimulus-Specific Adaptation (SSA). This effect can be recovered when the stimulus changes. In the auditory system SSA is a well-known phenomenon that appears at different levels of the mammalian auditory pathway. In this study, we explored the effects of adaptation to a particular stimulus on the auditory tuning curves of anesthetized rats. We used two sequences and compared the responses of each tone combination in these two conditions. First sequence consists of different pure tone combinations that were presented randomly. In the second one, the same stimuli of the first sequence were presented in the context of an adapted stimulus (adapter) that occupied 80% of sequence probability. The population results demonstrated that the adaptation factor decreased the frequency response area and made a change in the tuning curve to shift it unevenly toward the higher thresholds of tones. The local field potentials and multi-unit activity responses have indicated that the neural activities strength of the adapted frequency has been suppressed as well as with lower suppression in neighboring frequencies. This aforementioned reduction changed the characteristic frequency of the tuning curve.
Highlights
Neural adaptation is a common phenomenon which has been extensively observed in the mammalian sensory area such as visual [1,2], auditory [3,4,5], somatosensory [6], and so forth
Extracellular recordings from primary auditory cortex of urethane-anesthetized rats show that adaptation to specific stimulus near preferred or Characteristic Frequency (CF) causes a reduction in neural response and dwindle FRA
The results demonstrate that the suppression of neural activities was significant in the response of the adapter frequency
Summary
Neural adaptation is a common phenomenon which has been extensively observed in the mammalian sensory area such as visual [1,2], auditory [3,4,5], somatosensory [6], and so forth. Adaptation tends to suppress the neuronal activities in sensory systems. Adapting to the environment frequent stimuli such as light, smell, and sound is a vital brain function that the lack of it can be very disturbing. This mechanism causes some variations in neural properties against reputation to decrease the attention to the frequent stimulus. It leads to increase the neural sensitivity against unexpected changes for deviance detection [3]. The recent stimulus history affects the activities of cortical neurons. Recent studies have indicated that in an audio sequence the randomness of stimuli presentation affects significantly the neural responses of them [7]
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