How Human Brain Reacts to Active Thinking: A Conjunction Analysis Using fMRI

The human brain is the most complex biological organ in the creation of more than 100 billion neurons responsible for mind-blowing activities we witness on a day to day basis in our lifetimes. These activities are the result of both active and passive thinking. The distinction between active and passive thinking is extremely narrow comparable to a single strand of human hair. The aim of the present research work is to find the difference in brain activation on exposure to active thinking state, passive thinking state compared to baseline task using fMRI. The experiment targets to analyze brain activity when the teacher subjects are exposed to visuals to differentiate visual cognitive tasks associated with metaphorical thinking (active thinking) as well as non-metaphorical thinking (passive thinking). The aim is to establish the implementation of metaphorical thinking in enhancing the information processing ability among learners.


Introduction
Functional Magnetic imaging fMRI is a technique measuring brain activity by detecting the associated changes in blood flow. This technique, which is similar to MRI, uses the change in magnetization between oxygen-rich and oxygen-poor blood happening in the brain areas as the basic feature of measurement Cheryl et al [1]. The idea for foundations of magnetic resonance imaging was almost started in 1946 by Felix Bloch  who was at Stanford University studying liquids, and Edward Purcell  working on solids at Harvard University. Although they could have won Nobel Prizes for these discoveries, it was not until 1973, that successful nuclear magnetic resonance (NMR) was used to produce images. Finally, in the 1990s they discovered showing changes in blood oxygenation level could be considered with the use of MRI as a window opening a new generation of functional brain imaging techniques.
Blood Oxygenation Level-Dependent fMRI (BOLD fMRI) is a technique detecting the brain and neural activity indirectly, based on magnetic properties of hemoglobin Scott et al [2], It means that when Hbo and dHbo are placed in a magnetic field, dHbo will act as a contrast agent. Seong-Gi Kim and Kamil Ugurbil [3] discussed the mechanisms underlying the effects of deoxyhemoglobin concentration and the cerebral blood flow.
Stephen C Strother, Saman Sarraf, and Cheryl Grady [4] investigated using fMRI whether there is a specific reduction in the selectivity of brain activity during associative encoding in older adults, but not during item encoding, and whether this reduction predicts associative memory performance. Healthy young and older adults were scanned while performing an incidental-encoding task for pictures of objects and houses under item or associative instructions. An old/new recognition test was administered outside the scanner. They used agnostic canonical variates analysis and split-half resampling to detect whole-brain patterns of activation that predicted item vs. associative encoding for stimuli that were later correctly recognized. Older adults had poorer memory for associations than did younger adults, whereas item memory was comparable across groups. Associative encoding trials, but not item encoding trials, were predicted less successfully in older compared to young adults, indicating less distinct patterns of associative-related activity in the older group. Importantly, higher probability of predicting associative encoding trials was related to better associative memory after accounting for age and performance on a battery of neuropsychological tests. These results provide evidence that neural distinctiveness at encoding supports associative memory and that a specific reduction of selectivity in neural recruitment underlies age differences in associative memory. Price CJ, Friston KJ [5] used cognitive conjunction method. They designed the study such that a pair of tasks differ only by the processing component(s) of interest, the neural correlates of the process of interest are then associated with the common areas of activation for each task pair. There are two main advantages of cognitive conjunction relative to cognitive subtraction. The first is that it provides greater latitude for selecting baseline tasks because it is not necessary to control for all but the component of interest. Caplan D, Moo L [6] suggested that the cognitive conjunctions identify the areas in which differences between several pairs of tasks do not differ significantly. These are regions in which subtractive contrasts across a set of experimental -baseline task pairs yield differential vascular responses of equal magnitude and in which interactions of pairs of tasks do not occur. For example, in the present experiment the teacher participants are shown the baseline task followed by metaphorical thinking statements followed by baseline, then non metaphorical statements, baseline, metaphorical images, baseline then non-metaphorical images.
Thus, the conjunction method involves single cognitive operation comparing the experimental and the baseline task associated with different vascular activity in the brain regions.
In the BOLD fMRI, the change in the concentration of deoxy Hemoglobin (dHbo) is dynamically monitored. Changes and correlations between tasks (stimulation) and concentration of oxyhemoglobin (Hbo) will be considered. As a general fact, the more neural activities there are, the more tissue needs energy.
This will increase the consumption of Glucose and O2, increasing the blood flow and volume, while the local concentration of dHbo is decreasing which will produce the BOLD fMRI signals. This process will be repeated to the end and it should mention that BOLD fMRI signals are relevant to these three physiological concepts: Glucose and O2consumption, blood flow and vol-ume, and concentration of dHbo, respectively. Since the fMRI provides vast information which could be difficult to interpret, a variety of statistical approaches are used in the analysis of the fMRI data. The present research is mainly focused on studying the BOLD signals while the subjects are engaged in active thinking and passive thinking with respect to a baseline state.
As there are several methods of analysis available in the literature, the method chosen for fMRI data in the present scenario is General Linear Model (GLM) applied to estimate unknown regression parameters using CONN software first-level analysis. In this experiment, the subjects are exposed to four different

Methodology
The experiment was designed using E-prime 2 software which synchronizes with 3T Siemens Skyra mode l for studying fMRI images of the subjects. fMRI block design model was adopted to design the experiment. The main objective of the experiment is to find out the effect of rest vs task on performing subjects. All the subjects included in this study are teachers teaching Science subjects in Govt or Govt aided as well as private schools. To begin with, the experiment starts with a blank slide with a "#" symbol displayed at the center displayed for three seconds which is followed by the display of five slides depicting the above four conditions arranged randomly. The duration of each slide is fixed at 3 seconds. Standard techniques are used in acquiring images.
The following instructions as specified Siemens Skyra 3 TMRI scanner were adopted.  Similarly, subject as well as condition-specific analyses for ROIs for ROI -level analyses were carried out by co-registering the functional files to structural files both normalized in MNI-space.

Post-processing the data
Post-processing of the fMRI data acquired for each subject is tested based on the following hypotheses Is there a significant difference in BOLD signals between resting vs task 1 (Processing Metaphorical thinking -statements)?
Is there a significant difference in BOLD signals between resting vs task 2 (Processing non-Metaphorical thinking -statements)?
Is there a significant difference in BOLD signals between resting vs task 3 (Processing Metaphorical thinking images)?
Is there a significant difference in BOLD signals between resting vs task 4 (Processing non-Metaphorical thinking -images)?
In order to explain the variation of BOLD signals in the above-mentioned tasks, CONN uses Deionizing step. This

Discussion
Friston & Price [8] suggested that a valid conjunction analysis can be viewed in a brain map of activations as follows: 1) each voxel is significantly activated by two or more tasks, 2) each voxel is not significantly modulated by an interaction effect between tasks, and 3) the estimated relationships between each voxel and each task are not significantly different. According to Nichols et al [7] random sampling of the t-value distribution is used to test null hypotheses stating task A has no effect on task B if there is significant effect null hypotheses could be rejected.
t-values of a voxel identified in a conjunction analysis of two tasks should be more highly correlated across those tasks and within individuals than the correlation of t-values for voxels not identified in the conjunction analysis. Worsely [8] suggested that in a conjunction analysis, using a fixed-effect model, allows one to infer: (i) that every subject studied activated and (ii) that at least a certain proportion of the population would have shown this effect for the given conditions during the experiment. Recent neuro imaging evidence indicated that symbolic fractions experiment with fMRI by Ischebeck A, Schocke M, Delazer M [9] and non-symbolic proportions by Jacob SN, Nieder A [11] are processed within a frontoparietal network including the IPS. The results were in agreement with evidence obtained on whole number processing by (e.g., Dehaene S, Piazza M, Pinel P, Cohen L [13]. Arsalidou M, Taylor MJ [12]. Both these experiments suggest that both absolute and relative of magnitude information seem to be processed within this brain area.

Conclusions
fMRI experiment proved a concrete evidence showing activation in the frontal lobe left in all the subjects and in hippocampus regions of brain for the task baseline vs Metaphorical thinking though the experiment was conducted in all the subjects exposing them to visually process all the four different tasks with respect to the baseline. The idea of conjunctional analysis applied to this experiment might have simultaneously activated the voxel it was the relative activation was taken into account as it is impossible to ignore the activation caused by the other three tasks. Overall it could be concluded that the lesson plan implemented with metaphorical thinking statements influences the information processing ability of the learners.