Mismatch between electrocortical stimulation and electrocorticography frequency mapping of language

Area of Science:

• Neurosurgery
• Neurophysiology
• Epilepsy Research

Background:

• Electrocortical Stimulation Mapping (ESM) is standard for mapping eloquent cortex but can induce seizures and requires patient cooperation.
• Electrocorticography (ECoG) offers a potential alternative, but studies comparing it with ESM for language cortex mapping have yielded mixed results.
• Previous ECoG studies may underestimate language representation due to limited language tasks.

Purpose of the Study:

• To assess how different language tasks influence the agreement between ECoG and ESM for language cortex mapping.
• To compare ECoG language mapping during spontaneous conversation with ESM data in eight epilepsy patients.

Main Methods:

• ECoG and video data were analyzed during spontaneous conversation (speaking, listening, rest) and two language tasks (verb generation, picture naming).
• Power-frequency analysis was performed for each condition and task.
• The agreement between ESM and ECoG frequency mapping was quantified using sensitivity and specificity.

Main Results:

• ECoG demonstrated activation in and around established language areas during both spontaneous conversation and specific language tasks.
• A comparison of activated electrodes revealed high specificity but low sensitivity for ECoG mapping relative to ESM.
• Spontaneous language ECoG mapping did not enhance the concordance with ESM.

Conclusions:

• The agreement between ECoG and ESM for language cortex mapping remains suboptimal, even when incorporating spontaneous speech.
• Current ECoG language mapping techniques may not fully capture the extent of language representation identified by ESM.