Abstract

We present a lumped computational model of the thalamo–cortico–thalamic circuitry. The model
essentially consists of two modules: a thalamic module and a cortical module. The thalamic module
circuitry is a modified version of a classic neural mass computational model of the thalamic circuitry to
simulate cortical alpha rhythms and which we have used in previous research to study EEG abnormality
associated with Alzheimer’s Disease (AD). Here, we introduce a modified synaptic structure representing
a neuronal population in the thalamic model. Furthermore, the synaptic organisation and connectivity
parameter values in the model are based on experimental data reported from the dorsal Lateral Geniculate
Nucleus of different species. The cortical module circuitry is based on a recent work studying cortical brain
rhythms. We vary the synaptic connectivity parameters in the thalamic module of the model to simulate
the effects of AD on brain synaptic circuitry and study power within the alpha frequency bands. The power
and dominant frequencies of the model output are studied in three sub-bands within the alpha band:
lower alpha (7–9 Hz), middle alpha (9–11 Hz) and upper alpha (11–13 Hz). Such an analytical method
conforms to recent comparative EEG studies on young adults, healthy aged adults and MCI or early stage
AD patients. The results show a remarkable role of the synaptic connectivities in the inhibitory thalamic
cell populations on the alpha band power and frequency. Furthermore, the total number of active synapses
in the thalamic cell populations produces the slowing of alpha rhythms and a simultaneous decrease of
alpha band power in the brain as a result of AD.