Alexia and left homonymous hemianopia in a non-right-hander

Area of Science:

• Neuroscience
• Neurology
• Cognitive Science

Background:

• The disconnection hypothesis posits that language, handedness, and reading functions are typically lateralized to the same cerebral hemisphere.
• Understanding hemispheric lateralization is crucial for diagnosing and treating cognitive deficits following brain injury.

Observation:

• A non-right-handed patient presented with alexia without agraphia following a right occipital lobe infarction.
• Intracarotid amobarbital testing revealed left hemispheric dominance for speech functions in this patient.

Findings:

• The patient's alexia without agraphia could not be explained by the standard disconnection hypothesis.
• Findings suggest a potential dissociation of cognitive functions, with speech lateralized to the left hemisphere and reading/writing functions to the right hemisphere.

Implications:

• This case challenges established models of hemispheric lateralization for reading and language.
• It highlights the possibility of right-hemisphere dominance for reading and writing, even with left-hemisphere speech dominance.
• Further research is needed to explore the neuroplasticity and variability of cognitive function lateralization.