Through cognitive tasks certain brain areas are activated and also receive increased blood to them. This is modeled
through a state system consisting of two separate parts one that deals with the neural node stimulation and the other
blood response during that stimulation. The rationale behind using this state system is to validate existing analysis
methods such as DCM to see what levels of noise they can handle. Using the forward Euler's method this system
was approximated in a series of difference equations. What was obtained was the hemodynamic response for each
brain area and this was used to test an analysis tool to estimate functional connectivity between each brain area with
a given amount of noise. The importance of modeling this system is to not only have a model for neural response
but also to compare to actual data obtained through functional imaging scans.
Emotional tasks may result in a strong blood oxygen level-dependent (BOLD) signal in the amygdala in 5-
HTTLRP short-allele. Reduced anterior cingulate cortex (ACC)-amygdala connectivity in short-allele
provides a potential mechanistic account for the observed increase in amygdala activity. In our study, fearful
and threatening facial expressions were presented to two groups of 12 subjects with long- and short-allele
carriers. The BOLD signals of the left amygdala of each group were averaged to increase the signal-to-noise
ratio. A Bayesian approach was used to estimate the model parameters to elucidate the underlying
hemodynamic mechanism. Our results showed a positive BOLD signal in the left amygdala for short-allele
individuals, and a negative BOLD signal in the same region for long-allele individuals. This is due to the fact
that short-allele is associated with lower availability of serotonin transporter (5-HTT) and this leads to an
increase of serotonin (5-HT) concentration in the cACC-amygdala synapse.
KEYWORDS: Amygdala, Functional magnetic resonance imaging, Sensors, Signal processing, Hemodynamics, Neurotransmitters, Solids, Brain, Signal to noise ratio, Data acquisition
A negative blood oxygen level - dependent (BOLD) has been associated with a high concentration of GABA using Magnetic Resonance Spectroscopy and fMRI. Subjects with long-allele carriers have seen with high concentration of serotonin in Rostral Subgenual portion of the anterior cingulate cortex (rACC). In this paper, we investigate the effect of serotonin concentration on hemodynamic responses. Our results show a negative BOLD signal in rACC in the subjects with long-allele carriers. In contrast, the subjects with short-allele carriers showed positive BOLD signals in rACC. These results suggest that the serotonin transporter gene impacts the neuronal activity and eventually the BOLD signal similar to GABA.
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