Page 177 - AWSAR 2.0

functional changes and neural correlates of learning and memory were still not clear. At the time for preparing these patients for MRI acquisitions, one fundamental challenge was their inability to remember even
simple instructions told to keep
in mind during acquisition. To
understand the mechanism
behind these characteristic
deficits, in discussion with my
Ph.D. guide Prof. John P John,
we have developed two simple
forced choice discrimination
tasks to be performed during
the functional Magnetic
Resonance Imaging (fMRI)
and Magnetoencephalography
(MEG) acquisitions. During
the first task, the encoding of visual stimulus happens incidentally while performing a living/ non-living discrimination task in absence of specific instructions to remember the stimulus. While performing the second task, the retrieval of the encoded stimulus is measured intentionally, where the individual is specifically instructed to recall whether the stimulus was shown earlier during the process of incidental encoding.
Functionally, fMRI analysis showed brain areas corresponding to encoding and retrieval having reduced brain activations in AD and increased activations in MCI in comparison to healthy participants. The MEG analysis showed a continuum of activation; highest in
Mr. Himanshu Joshi || 153
healthy participants, intermediate in patients with MCI and lowest in patients with mild AD corresponding to both, encoding and retrieval tasks. The structural MRI findings and fMRI/
MEG activation alterations are closely associated to cognitive deficits, especially episodic memory deficits assessed by the incidental encoding and intentional retrieval task as well as cognitive assessments performed outside the scanner. The fMRI as indirect and MEG being direct measure of neuronal activity supports the above results and suggests a possible compensatory mechanism in the form of
increased oxygen consumption and blood flow in brain regions responsible for episodic memory during early Alzheimer’s disease.
These findings can be used to develop a mobile app for rapidly increasing older population in India, where only one out of ten dementia cases receive a diagnosis and nine others lives like “Smruti Kaki”. This may further assist at risk elders in reaching the clinician at the earliest to avoid the delay in diagnosis. Furthermore, with the help of the mobile app database, we can standardize the cut-offs to specifically target those individuals who are vulnerable to the cognitive decline associated with Alzheimer’s pathology.
Structurally, the patients with mild AD showed volumetric reductions in those regions of the brain, which are involved in memory, attention and concentration in comparison to healthy elderly participants.