1 hz rTMS over the right prefrontal cortex reduces vigilant attention to unmasked but not to masked fearful faces.

BACKGROUND: Recent repetitive transcranial magnetic stimulation (rTMS) research in healthy subjects suggests that the emotions anger and anxiety are lateralized in the prefrontal cortex. Low-frequency rTMS over the right prefrontal cortex (PFC) shifts the anterior asymmetry in brain activation to the left hemisphere and reduces anxiety. The same rTMS technique results in enhanced anger-related emotional processing, observed as elevations in attention for angry faces. The current study used low-frequency rTMS over the right PFC and indexed selective attention to fearful faces, hypothesizing a reduction in attention for fearful faces, i.e., a reversal of the latter effect. METHODS: In a placebo-controlled design, 1 Hz rTMS at 130% of the individual motor threshold (MT) was applied continuously over the right PFC of eight healthy subjects for 20 minutes. Effects on motivated attention were investigated by means of an emotional Stroop task, indexing selective attention to masked and unmasked fearful faces. RESULTS: Vigilant attention for masked and unmasked fearful faces was observed after placebo stimulation. As hypothesized, rTMS reduced the vigilant emotional response to the fearful face, but only in the unmasked task. CONCLUSIONS: These data provide further support for the lateralization of the emotions anger and anxiety in the prefrontal cortex. In addition, the absence of an effect for masked fearful faces suggests that changes in emotional processing after a single session of rTMS predominantly involve the cortical affective pathways.     

Peripheral attention versus central fixation: Modulation of the visual activity of prelunate cortical cells of the rhesus monkey

Single unit activity was monitored in the prelunate gyrus of monkeys trained to execute or suppress goal-directed saccades to a peripheral target in the presence or absence of a central fixation spot. Throughout the experiments in the dimming paradigm was used. We observed the previously reported spatially selective enhancement of the visual on-response and the extra activation before saccades to a continuously visible target. However, we also observed a sudden increase of activity when the central fixation spot was extinguished in the presence of a peripheral target which the monkey decided not to look at, although he could detect its dimming correctly. This activity is also spatially selective: it occurs only if the peripheral target is within the receptive field of the cell. The presence or absence of just any foveal spot, which is behaviourally not relevant, does not make any difference. The activity occurs about 220 ms after fixation point offset. Thus it can be interpreted as a sign of the animal having directed attention to the peripheral target and/or having stopped active fixation being ready for the next goal-directed saccade without necessarily executing it.     

Prepare for conflict: EEG correlates of the anticipation of target competition during overt and covert shifts of visual attention

When preparing to make a saccadic eye movement in a cued direction, perception of stimuli at the target location is enhanced, just as it is when attention is covertly deployed there. Accordingly, the timing and anatomical sources of preparatory brain activity accompanying shifts of covert attention and saccade preparation tend to exhibit a large degree of overlap. However, there is evidence that preparatory processes are modulated by the foreknowledge of visual distractor competition during covert attention, and it is unknown whether eye movement preparation undergoes equivalent modulation. Here we examine preparatory processes in the electroencephalogram of human participants during four blocked versions of a spatial cueing task, requiring either covert detection or saccade execution, and either containing a distractor or not. As in previous work, a typical pattern of spatially selective occipital, parietal and frontal activity was seen in all task versions. However, whereas distractor presence called on an enhancement of spatially selective visual cortical modulation during covert attention, it instead called on increased activity over frontomedial oculomotor areas in the case of overt saccade preparation. We conclude that, although advance orienting signals may be similar in character during overt and covert conditions, the pattern by which these signals are modulated to ameliorate the behavioral costs of distractor competition is highly distinct, pointing to a degree of separability between the overt and covert systems.