Hearing syllables by seeing visual stimuli.

Currently it is discussed whether the same cortical areas are activated during the imagination of as during the actual presentation of specific stimuli. Some argue that mostly the secondary but not the primary sensory areas are active during imagination. Using functional magnetic resonance imaging we explored whether auditory verbal imagery of syllables has sufficient power to evoke haemodynamic responses in the auditory cortex. To overcome the detrimental effects of scanner noise, one group of subjects was trained to vividly imagine hearing a syllable while a flashlight was presented. A control group did not receive this training. We found that only the trained group revealed haemodynamic responses in the auditory cortex during auditory imagination while the control group showed no activation within the auditory cortex. Peak activations during auditory verbal imagery are located bilaterally within the superior temporal gyrus region in the vicinity of the planum temporale. While these secondary auditory areas are active during auditory verbal imagery, there was no activation in Heschl's gyrus. We hypothesize that auditory verbal imagery is associated with haemodynamic responses in secondary auditory and not primary auditory areas.