یک مطالعه fMRI برای بررسی مدولاسیون شناختی از مناطق مغز در ارتباط با پردازش عاطفی محرک های بصری

Brain regions modulated by cognitive tasks during emotional processing were investigated using fMRI. Participants performed indirect and direct emotional processing tasks on positive and negative faces and pictures. We used a multivariate technique, partial least squares (PLS) to determine spatially distributed patterns of brain activity associated with different tasks and stimulus conditions, as well as the interaction between the two. The pattern of brain activity accounting for the most task-related covariance represented a task×stimulus interaction and distinguished indirect processing of pictures and direct processing of faces from direct processing of pictures and indirect processing of faces. The latter two conditions were characterised by limbic (e.g. amygdala, insula, thalamus) and temporal lobe activity, in addition to greater activity in the ventral prefrontal cortex. Indirect and direct processing of pictures and faces, respectively, were represented by more dorsal prefrontal and parietal activity. These findings indicate that brain activity during processing of emotional content is critically dependent on both the type of stimulus and processing task. In addition, these results support the idea that the pattern of activity in the emotional network can be influenced in a ‘top–down’ fashion via cognitive factors such as attentional control, and as such, have important clinical implications for emotional disorders, such as depression and anxiety.

Neuroimaging techniques such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have been used to map brain regions associated with the visual processing of emotional stimuli in healthy adults. Most of these studies have used either emotional faces or pictures in a variety of paradigms that manipulate subjects’ attention and physiological response to the emotional content of the stimuli in order to isolate activity. A major theme concerns the role of the amygdala, and although this brain region is important for certain types of emotional processing, some studies failed to find evidence for its involvement. This variability may be because the research strategies have been narrowly linked to particular tasks and stimuli. The type of task and the stimuli utilised are very important, as different aspects of emotional processing have been shown to modulate different brain regions. There has been no attempt to date, however, to combine different types of stimuli as well as emotional processing tasks to determine how stimulus features and processing task together affect activity in brain regions important for emotion, including the amygdala. This issue is the subject of the current experiment.

Brain activity associated with the emotional processing of faces and pictures occurred in brain regions that have previously been implicated in various emotional processing paradigms (e.g. amygdala, insula, prefrontal cortex and anterior cingulate). The functional network appears to recruit higher cortical structures, which may modulate activity in limbic regions, depending on the type of stimulus and task. For example, the amygdala and related regions (thalamus, insula, rostral anterior cingulate, ventral and inferior prefrontal cortex) have been suggested to form a “primitive” neural system for processing emotional stimuli with biological significance, such as fearful/angry faces. Cognitive tasks demanding increased attention have been shown to attenuate activity in these brain regions [20] and increase activity in dorsal areas. Thus, the results of the task and seed analyses in the current study suggests that these regions form an “emotional” network that includes both limbic regions and the prefrontal regions that modulate them, as well as the areas important for visual analysis (e.g. fusiform gyrus). Our results also point out that this effect behaves differently for pictures and faces. In particular, emotional faces trigger the limbic regions in this network in an automatic, perhaps pre-attentive fashion, whereas emotional pictures trigger them only when attention is focused on the emotional content. These findings are important from a clinical perspective because it lends support to the idea that the intricate nature of the interaction between these regions may be compromised by various mood and cognitive disorders (e.g. depression and Alzheimer’s disease). Further research into the nature of this interaction could contribute to a better understanding of the impairments in information processing associated with these disorders.