Auditory-evoked potentials to frequency increase and decrease of high- and low-frequency tones.
OBJECTIVE
To define cortical brain responses to large and small frequency changes (increase and decrease) of high- and low-frequency tones.


METHODS
Event-Related Potentials (ERPs) were recorded in response to a 10% or a 50% frequency increase from 250 or 4000 Hz tones that were approximately 3 s in duration and presented at 500-ms intervals. Frequency increase was followed after 1 s by a decrease back to base frequency. Frequency changes occurred at least 1 s before or after tone onset or offset, respectively. Subjects were not attending to the stimuli. Latency, amplitude and source current density estimates of ERPs were compared across frequency changes.


RESULTS
All frequency changes evoked components P(50), N(100), and P(200). N(100) and P(200) had double peaks at bilateral and right temporal sites, respectively. These components were followed by a slow negativity (SN). The constituents of N(100) were predominantly localized to temporo-parietal auditory areas. The potentials and their intracranial distributions were affected by both base frequency (larger potentials to low frequency) and direction of change (larger potentials to increase than decrease), as well as by change magnitude (larger potentials to larger change). The differences between frequency increase and decrease depended on base frequency (smaller difference to high frequency) and were localized to frontal areas.


CONCLUSIONS
Brain activity varies according to frequency change direction and magnitude as well as base frequency.


CONCLUSIONS
The effects of base frequency and direction of change may reflect brain networks involved in more complex processing such as speech that are differentially sensitive to frequency modulations of high (consonant discrimination) and low (vowels and prosody) frequencies.
Pratt
Hillel
H
Evoked Potentials Laboratory, Behavioral Biology, Gutwirth Building, Technion-Israel Institute of Technology, Haifa 32000, Israel. hillel@tx.technion.ac.il
Starr
Arnold
A
Michalewski
Henry J
HJ
Dimitrijevic
Andrew
A
Bleich
Naomi
N
Mittelman
Nomi
N
D000161:Acoustic Stimulation / Q000379:methods; D000293:Adolescent; D001303:Auditory Cortex / Q000502:physiology*; D001931:Brain Mapping; D004569:Electroencephalography / Q000379:methods; D004585:Electrooculography / Q000379:methods; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D025341:Principal Component Analysis; D011571:Psychoacoustics; D011930:Reaction Time / Q000502:physiology; D013057:Spectrum Analysis / Q000379:methods; D055815:Young Adult