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MCAT

Unit 4: Lesson 1

Foundations of behavior passages

Patient with a missing cerebellum

Problem

In the September of 2014, a 24-year-old woman entered a clinic reporting symptoms of dizziness and nausea. Upon a Computerized Tomography (CT) scan, physicians were fascinated to discover that the patient completely lacked a cerebellum. The empty space in her brain was filled with cerebrospinal fluid, which is important for immune processes and the prevention of shock trauma to the spine. See Figure 1.
Figure 1. The CT scan of the patient. Notice the missing cerebellum on the right side.
The cerebellum is a portion of the hindbrain that is involved in balance, movement, and fine motor control. Recent research suggests that it might also be involved in the fear and pleasure response. The cerebellum contains a significant amount of Purkinje fibers, a specialized neuron hallmarked by its unique dendrite layer. Due to this distinctive structure, Purkinje fibers are able to accommodate more synaptic information than any other type of neuron. Because of this specialization, they exist in greater quantities where speed and efficiency of neural signaling are critical. Purkinje fibers are often connected by gap junctions or desmosomes.
In an effort to explore the potential further effects of a missing cerebellum, scientists performed neurosurgery on male mice to remove the cerebellum. The mice were divided into two groups: a control group that underwent the operation and another that was sham-operated. The mice were then tested for a number of factors, including hormonal levels and sensory awareness. Vision, smell, and taste abilities of the experimental group were not significantly different than the control group. Further, testosterone and ADH levels were no different than average. However, cortisol, the hormone that instigates the fear response, had significantly lower levels in the experimental group.
Source: Thompson, H. (2014). Woman of 24 found to have no cerebellum in her brain. NewScientist Health. Issue 2986.
What is a viable prediction from the mice study?
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