The thalamus has a role in the basal ganglia system but this is poorly understood. The thalamus has been thought of as a "relay" that just forwards signals to the cerebral cortex. But research suggests that thalamus is more selective. Many different functions are linked to regions of the thalamus. This is the case for most sensory systems (except the olfactory system), such as the auditory, somatic sensory system, visceral, eating and visual systems. There specific lesions cause specific sensory deficits. A big role of the thalamus is to support the motor and language systems. Much of the circuitry for these systems is shared with the thalamus. The thalamus is "functionally connected" to the hippocampus. This is part of the hippocampal system which is crucial for human episodic event memory.