Professional and Linguistic Assessments Board (PLAB) Practice Exam

Which area of the brain is primarily affected by lesions leading to sensory disturbances?

1. Frontal lobe

2. Thalamus

3. Occipital lobe

4. Brainstem

The correct answer is: Thalamus

The thalamus is often referred to as the brain's sensory relay station because it plays a critical role in processing and transmitting sensory information to the appropriate areas of the cerebral cortex. Sensory disturbances, such as loss of sensation or altered sensory perceptions, commonly occur when there are lesions or damage within the thalamic region. This is due to its connections with almost all sensory modalities, including touch, pain, temperature, vision, and hearing. When lesions affect the thalamus, the flow of sensory information to the cortex can be disrupted, leading to a variety of sensory disturbances. For example, damage to specific thalamic nuclei can result in sensory loss on the opposite side of the body, a condition known as thalamic pain syndrome, where patients experience chronic and sometimes painful sensations. While other areas of the brain, such as the frontal lobe, occipital lobe, and brainstem, can also be involved in sensory processing, the thalamus is the primary structure specifically responsible for relaying and processing sensory information. Hence, lesions in this area have a direct and significant impact on sensory disturbances.