Face recognition and cortical responses show similar sensitivity to noise spatial frequency.
To find cortical correlates of face recognition, we manipulated the recognizability of face images in a parametric manner by masking them with narrow-band spatial noise. Face recognition performance was best at the lowest and highest noise spatial frequencies (NSFs, 2 and 45 c/image, respectively), and degraded gradually towards central NSFs (11-16 c/image). The strength of the 130-180 ms neuromagnetic response (M170) in the temporo-occipital cortex paralleled the recognition performance, whereas the mid-occipital response at 70-120 ms acted in the opposite manner, being strongest for the central NSFs. To noise stimuli without faces, M170 was small and rather insensitive to NSF, whereas the mid-occipital responses resembled closely the responses to the combined face and noise stimuli. These results suggest that the 100 ms mid-occipital response is sensitive to the central spatial frequencies that are critical for face recognition, whereas the M170 response is sensitive to the visibility of a face and closely related to face recognition.
Brain Research Unit, Low Temperature Laboratory, Helsinki University of Technology, PO Box 2200, FIN-02015, Espoo, Finland. topi.tanskanen@hut.fi
Topi
T
Tanskanen
Risto
R
Näsänen
Teresa
T
Montez
Juha
J
Päällysaho
Riitta
R
Hari
D000328:Adult; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005145:Face / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009778:Occipital Lobe / Q000502:physiology; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D013702:Temporal Lobe / Q000502:physiology; D014793:Visual Cortex / Q000502:physiology*