After eating, the human brain senses a biochemical change and then signals satiation, but precisely when this occurs is unknown. Even for well-established physiological systems like glucose-insulin regulation, the timing of interaction between hormonal processes and neural events is inferred mostly from blood sampling. Recently, neuroimaging studies have provided in vivo information about the neuroanatomical correlates of the regulation of energy intake. Temporal orchestration of such systems, however, is crucial to the integration of neuronal and hormonal signals that control eating behaviour. The challenge of this functional magnetic resonance imaging study is to map not only where but also when the brain will respond after food ingestion. Here we use a temporal clustering analysis technique to demonstrate that eating-related neural activity peaks at two different times with distinct localization. Importantly, the differentiated responses are interacting with an internal signal, the plasma insulin. These results support the concept of temporal parcellation of brain activity, which reflects the different natures of stimuli and responses. Moreover, this study provides a neuroimaging basis for detecting dynamic processes without prior knowledge of their timing, such as the acute effects of medication and nutrition in the brain.
In a functional magnetic resonance imaging (fMRI) study, a novel connectivity analysis method termed within-condition interregional covariance analysis (WICA) was introduced for investigation into brain modulation during tongue movement and reading Chinese pinyins and logographic characters. We found that performing a horizontal tongue movement task generated a specific brain module with hierarchical orders of neural computation. Such functional modularity was further examined during both overt and silent Chinese reading tasks. Our results showed that overt pinyin reading was associated with the following distributed regions involved in tongue movement: the primary motor cortex (M1), the supplementary motor area (SMA), Broca's area, and Wernicke's area. Furthermore, we have used the WICA and demonstrated task-dependent covariance patterns that are strongly associated with the M1 mouth/tongue region, in which the Broca-Wernicke pathway is implicated in a meaning access procedure based on assembled phonology, while the SMA-Broca pathway is implicated in a meaning access procedure based on addressed phonology. Our functional connectivity analysis of the neural pathway involved in language processing may provide a basis for future studies of the dynamic neural network associated with language learning and reading in both developmental and disease conditions.
Obsessive-compulsive disorder may not be an anxiety disorder, but more accurately a disgust disorder. Our lab previously showed that the insula has a larger response to disgusting pictures in patients with OCD 1, but other studies found that the insula responded equally to pictures evoking fear 2, 3. While our study used pictures of contamination (for example, a dirty toilet) to evoke disgust, the other studies used both pictures of contamination and of mutilations (for example, a burn victim). We therefore decided to test the response to these two types of disgusting pictures seperately. (We also included fear-inducing pictures of attacks).
In the end, this experiment did not explain the difference between our results and those from the other lab, but we confirmed that we can measure a selective response to disgust in the insula. Most interestingly adding the mutilation pictures allowed us to show how activity in different parts of the brain depends on different emotional ratings of the pictures.
The figure shows brain activation for our three picture types, compared with neutral pictures. You can see activation in the insula (INS) for contamination and mutilation, but not for fear. Also notice that another region toward the back of the brain, the occipito-temporal cortex (OTC), is more activated for the mutilation and fear pictures, but less for the contamination pictures. This part of the brain is involved in visual processing, and previous research suggests it is more active when viewing emotionally arousing pictures.
We also collected ratings for the pictures we showed our volunteers. The pictures already had general emotional ratings, and we also collected ratings for emotional categories, such as disgust. Briefly, our ratings showed that people found the mutilation and contamination pictures more disgusting than the fear pictures, and that they found the fear and mutilation pictures more arousing than the disgust pictures. We noted how these ratings seemed to correspond to our brain activation, so we used statistical analysis to see if the two were related. We found strong correlations between the disgust rating and activity in the insula, and between the arousal rating and activity in the OTC (although the former was only marginally statistically significant because we had so few examples to test). When we tried these correlations the other way round, we did not find significant correlations between disgust rating and activity in the OTC or between arousal rating and activity in the insula. This suggests that there is what psychologists call a "double dissociation" between processing of disgust and of general emotional arousal.
We were only able to test these correlations because we had more than two different types of pictures with varying degrees of disgust and emotional arousal. It appears that the mutilation pictures evoke brain responses similar to those seen for both fear and disgust, so perhaps these pictures evoke the emotion "horror"
This study was funded by the National Alliance for Research in Schizophrenia and Depression (NARSAD).
We used Lang’s biphasic theory of emotion (1985) and bio-informational theory of emotional imagery, to investigate exercisers’ and non-exercisers’ verbal and physiological (cortical activation, heart rate, and skin conductance) reactions to exercise stimuli (pictures and imagery scripts). We compared and contrasted brain activity between women who enjoy running and have been running for the previous five years (terminators) and women who dislike running and do not intend to engage in any physical activity in response to exercise stimuli (precontemplators). Differences were found between the groups, and are currently being prepared for publication.
We have located and tested a full-sized keyboard for use in fMRI experiments. Composed of conductive plastics with minimal metallic content, the Virtually Indestructible Keyboard (VIK; available online from GrandTec USA or its distributors, including RadioShack) was believed to be a feasible alternative to costly fiber-optic response systems.
Our analyses indicate that the keyboard, with or without continuous keypresses, had no effect upon the BOLD signal (James, He, and Liu; ISMRM conference 2003). The VIK offers a vast number of distinct keypress responses – including a numeric keypad. Combined with its relative inexpense, the VIK is an ideal tool for acquiring behavioral data from subjects within the scanner environment.
Note: no funding has been nor will be accepted from GrandTec USA or its distributors.
A functional MRI study compared activation in the red nucleus to that in the lateral cerebellar dentate nucleus during passive and active tactile discrimination tasks. The study pursued recent neuroimaging results suggesting that the cerebellum may be more associated with sensory processing than with the control of movement for its own sake. Because the red nucleus interacts closely with the cerebellum, the possibility was examined that activity in red nucleus might also be driven by the requirement for tactile sensory processing with the fingers rather than by finger movement alone. The red and dentate nuclei were about 300% more active (a combination of activation areas and intensities) during passive (non-motor) tactile stimulation when discrimination was required than when it was not. Thus, the red nucleus was activated by purely sensory stimuli even in the absence of the opportunity to coordinate finger movements or to use the sensory cues to guide movement. The red and dentate nuclei were about 70% more active during active tactile tasks when discrimination was required than when it was not (i.e., for simple finger movements alone). Thus, the red nucleus was most active when the fingers were being used for tactile sensory discrimination. In both the passive and active tactile tasks, the observed activation had a contralateralized pattern, with stronger activation in the left red nucleus and right dentate nucleus. Significant covariation was observed between activity in the red nucleus and the contralateral dentate during the discrimination tasks and no significant correlation between the red nucleus and the contralateral dentate activity was detected during the two non-discrimination tasks. The observed interregional covariance and contralateralized activation patterns suggest strong functional connectivity during tactile discrimination tasks. Overall, the pattern of findings suggests that the activity in the red nucleus, as in the lateral cerebellum, is more driven by the requirements for sensory processing than by motor coordination per se.