Intracerebral Electrical Stimulation of the Left Occipito-Temporal Cortex Induces Pure Alexia

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Neurology

Background:

• The left ventral occipito-temporal cortex (VOTC) is recognized for its role in processing visual word forms.
• Previous functional magnetic resonance imaging (fMRI) studies suggest its importance, but direct causal evidence for reading networks is lacking.

Purpose of the Study:

• To investigate the causal role of the left VOTC in the reading network using direct electrical stimulation (DES).
• To determine if the VOTC contains word-selective neural representations critical for reading.

Main Methods:

• Direct electrical stimulation (DES) was applied to the left VOTC in a patient with refractory epilepsy undergoing electrode implantation.
• Reading abilities, including single-word reading and letter identification, were assessed during DES.
• Intracerebral electrophysiological frequency tagging was used to identify word-selective neural responses.

Main Results:

• DES of the left posterior occipito-temporal sulcus transiently impaired single-word reading, while letter-by-letter reading remained possible.
• Reading single letters rapidly was also affected, indicating a broader reading impairment.
• DES abolished word-selective neural responses and affected remote VOTC activity, while other cognitive functions remained intact.

Conclusions:

• The left VOTC is a critical node in the cortical reading network, demonstrating a causal role in visual word processing.
• The findings provide evidence for word-selective representations within the left VOTC essential for reading ability.