Researchers have reported that patients with temporal lobe epilepsy (TLE), which can cause reasoning, memory, attention, and language function problems, show deficiencies for perceiving and reproducing their own voice pitch.
The research paper, “Temporal Lobe Epilepsy Alters Auditory-motor Integration For Voice Control,” was published in the journal Scientific Reports.
Twenty-eight patients with TLE (10 females and 18 males) and 28 healthy participants (also 10 females and 18 males) were included in the study. In a sound proof room, participants heard their voice feedback with a gain of ½ or 2 semitones upward, and then were asked to reproduce the sound during a test known as frequency-altered feedback (FAF).
Healthy patients tended to adjust their vocal pitch in the opposite direction returning to their normal voice. However, TLE patients produced even larger vocal responses relative to the intensity of their vocal output. The enhanced vocal responses to FAF show that patients have problems in auditory-motor brain integration for voice control, which indicates that they are unable to correct vocal pitch.
During the test, researchers also monitored brain response by electroencephalography (EEG). They found that very small voltages generated in the brain structures in response to the sound, called event-related potentials (ERPs), were lower in TLE patients. The effect was even more significant with increased duration of the disease. In addition, other parameters measured by EEG showed that neuronal signal propagation between cortical regions are slower in patients.
Together, the data suggest that the functional neural network that supports auditory-motor processing of pitch feedback errors is affected in patients with TLE.
Although the findings provide the first evidence that patients with TLE present atypical auditory-motor integration for vocal pitch regulation, the authors could not exclude the interference of antiepileptic therapy in their findings.
In the report, researchers explained that most of the TLE patients in the study were taking multiple drug therapies, making it impossible to rule out the possibility that observed changes in the auditory-motor integration for voice control could be partially due to the long-term impact of antiepileptic drugs (AEDs).