Decreased coherence in the model of the dorsal visual pathway associated with Alzheimer's disease

Abstract

Decreased coherence in electroencephalogram (EEG) has been reported in Alzheimer's disease (AD) experimentally, which could be considered as a typical electrophysiological characteristic in AD. This work aimed to investigate the effect of AD on coherence in the dorsal visual pathway by the technique of neurocomputation. Firstly, according to the hierarchical organization of the cerebral cortex and the information flows of the dorsal visual pathway, a more physiologically plausible neural mass model including cortical areas v1, v2, and v5 was established in the dorsal visual pathway. The three interconnected cortical areas were connected by ascending and descending projections. Next, the pathological condition of loss of long synaptic projections in AD was simulated by reducing the parameters of long synaptic projections in the model. Then, the loss of long synaptic projections on coherence among different visual cortex areas was explored by means of power spectral analysis and coherence function. The results demonstrate that the coherence between these interconnected cortical areas showed an obvious decline with the gradual decrease of long synaptic projections, i.e. decrease in descending projections from area v2 to v1 and v5 to v2 and ascending projection from area v2 to v5. Hopefully, the results of this study could provide theoretical guidance for understanding the dynamical mechanism of AD.

Figure 1

Diagram of the model sketch for the dorsal visual pathway. This neural mass model included three interconnected cortical areas of v1, v2, and v5. Each cortical area is composed of four neuron populations of PY, eIN, sIN and fIN. Black arrows represent excitatory synaptic connection and black rounds represent inhibitory synaptic connection in the single cortical area. Green arrows denote long synaptic projections from area v1 to v2 and v5; red arrows denote long synaptic projections from area v2 to v1 and v5; purple arrows denote long synaptic projections from area v5 to v1 and v2; orange-colored arrows denote Gaussian white noise which represents exogenous afferent from other connected areas not included in this model.

Figure 2

PSD of areas v1 (blue dotted line), v2 (red dashed line) and v5 (pink solid line) without long synaptic projections between the three cortical areas.

Figure 3

The first and second columns are PSD of areas v2 and v1, respectively. The coherence function between the two areas was delineated in the third column. From top to bottom, the parameters of long synaptic projection from v2 to v1 were in turn = 20, 15, 10, 5 and 0.

Figure 4

Coherence between areas v2 and v1 with $k_{21}$ changing from 20 to 0.

Figure 5

The first and second columns are PSD of areas v5 and v2, respectively. The coherence function between the two areas was delineated in the third column. From top to bottom, the parameters of long synaptic projection from v5 to v2 were in turn = 25, 20, 15, 5 and 0.

Figure 6

Coherence between areas v5 and v2 with $k_{52}$ changing from 30 to 0.

Figure 7

The first and second columns are PSD of areas v2 and v5, respectively. The coherence function between the two areas was delineated in the third column. From top to bottom, the parameters of long synaptic projection from v2 to v5 were in turn = 50, 35, 20, 5 and 0.

Figure 8

Coherence between areas v2 and v5 with $k_{25}$ changing from 50 to 0.