Why did Thompson conclude that eyeblink conditioning depends on the lateral interpositus nucleus, instead of the red nucleus? A. Inactivating the red nucleus failed to suppress responses. B. Inactivating the red nucleus suppressed responses, and after the rabbit recovered, it had to learn the same as a rabbit that had never been trained. C. Inactivating the red nucleus suppressed responses to some stimuli but not others. D. Inactivating the red nucleus suppressed responses, but did not prevent learning.
The correct answer and explanation is:
The correct answer is A. Inactivating the red nucleus failed to suppress responses.
Eyeblink conditioning, a form of classical conditioning, is a widely studied phenomenon in neuroscience. In this process, a neutral stimulus, such as a tone, is paired with an unconditioned stimulus, such as a puff of air to the eye, which causes the rabbit to blink. Over time, the rabbit learns to blink in response to the tone alone.
Thompson’s experiments aimed to identify the neural structures involved in this form of conditioning. He focused on the lateral interpositus nucleus (LIP) and the red nucleus, both of which are part of the cerebellar and brainstem pathways involved in motor control.
Thompson’s conclusion that the lateral interpositus nucleus (LIP) is crucial for the conditioned eyeblink response was supported by the following observations:
- Inactivation of the lateral interpositus nucleus completely disrupted the conditioned eyeblink responses, suggesting that this area plays a direct role in storing and executing the conditioned motor response.
- When the red nucleus was inactivated, it did not stop the animal from performing the conditioned blink response. This indicated that the red nucleus was not as critical for the expression of the conditioned response.
- The key finding was that inactivating the red nucleus failed to suppress responses (answer A), which helped Thompson eliminate it from the critical network. In contrast, inactivating the lateral interpositus nucleus not only suppressed the responses but also prevented learning, highlighting its essential role in both the acquisition and expression of the conditioned blink.
Thompson’s work established that the lateral interpositus nucleus, rather than the red nucleus, is involved in the learning and execution of conditioned eyeblink responses.