Evaluating the feasibility of cognitive impairment detection in Alzheimer’s disease screening using a computerized visual dynamic test

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Evaluating the feasibility of cognitive impairment detection in Alzheimer’s disease screening using a computerized visual dynamic test

• Eduardo Perez-Valero,
• Christian A. Morillas Gutierrez,
• Miguel Angel Lopez-Gordo &
• Samuel López Alcalde 

Journal of NeuroEngineering and Rehabilitation volume 20, Article number: 43 (2023) Cite this article

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Abstract

Background

Alzheimer’s disease (AD) is a neurodegenerative disease without known cure. However, early medical treatment can help control its progression and postpone intellectual decay. Since AD is preceded by a period of cognitive deterioration, the effective assessment of cognitive capabilities is crucial to develop reliable screening procedures. For this purpose, cognitive tests are extensively used to evaluate cognitive areas such as language, attention, or memory.

Methods

In this work, we analyzed the potential of a visual dynamics evaluation, the rapid serial visual presentation task (RSVP), for the detection of cognitive impairment in AD. We compared this evaluation with two of the most extended brief cognitive tests applied in Spain: the Clock-drawing test (CDT) and the Phototest. For this purpose, we assessed a group of patients (mild AD and mild cognitive impairment) and controls, and we evaluated the ability of the three tests for the discrimination of the two groups.

Results

The preliminary results obtained suggest the RSVP performance is statistically higher for the controls than for the patients (p-value = 0.013). Furthermore, we obtained promising classification results for this test (mean accuracy of 0.91 with 95% confidence interval 0.72, 0.97).

Conclusions

Since the RSVP is a computerized, auto-scored, and potentially self-administered brief test, it could contribute to speeding-up cognitive impairment screening and to reducing the associated costs. Furthermore, this evaluation could be combined with other tests to augment the efficiency of cognitive impairment screening protocols and to potentially monitor patients under medical treatment.

Background

Dementia is an umbrella term used to describe the loss of cognitive functioning that affects individuals to the extent of interfering with daily-life activities [1]. Presently, around fifty million people live with dementia and the prevalence is expected to almost triple by 2050 owing to the aging of the global population [2]. Among the diseases that cause dementia, Alzheimer’s disease (AD) is the most common, since it represents between 60% and 80% of the cases [2]. AD is a neurodegenerative disease that affects multiple cognitive areas such as memory, orientation, or language [3]. Although the first case of AD was reported in 1901, its etiology still remains undetermined. Nonetheless, researchers have identified two main hallmarks linked to AD: amyloid plaques and neurofibrillary tangles [4]. The former are protein deposits that lose their standard structure and accumulate around the neurons, whilst the latter are thickened fibrils surrounding their nucleus. Both structures damage the neuronal processes and start to form more than ten years before the impairment is notable. On the other hand, mild cognitive impairment (MCI) refers to a transitional stage between normal aging and AD [5]. MCI patients experience minor memory losses which do not interfere with daily-life activities. However, they transition to AD faster than healthy individuals of the same age. In this context, although there is no cure for AD, medical treatment can contribute to controlling the progression of the disease and to delaying cognitive decline [6]. In this context, early detection is crucial for the wellness expectations of the patients.

With this in mind, primary healthcare represents the front-line for the detection of cognitive impairment before more complex procedures such as magnetic resonance imaging [7], positron emission tomography [8], or cerebro-spinal fluid analysis [9] are conducted. In this respect, cognitive tests have been extensively used to detect cognitive impairment via the assessment of the cognitive areas affected earlier in the course of AD, such as visuo-spatial ability, verbal fluency, and episodic memory [10,11,12,13]. Typically, cognitive tests are incorporated into test batteries in order to evaluate multiple cognitive areas in a single session [14, 15]. The most popular test batteries are the mini-mental state examination [16] and the Montreal cognitive assessment [17], although other evaluations such as the Test your memory assessment [18] and the Mini-Cog [19] have been proposed.

In this connection, traditional cognitive tests like the Clock-drawing test (CDT) [20], the animal naming test [21], or the abbreviated mental test [22], focus mainly on memory and executive functioning. Therefore, other cognitive areas affected early in the AD course, such as visual processing, may be overlooked. For the past decade, multiple works have reported reduced performance of AD patients in cognitive tests involving visual processing. For instance, [23] applied the theory of visual attention to the results of a letter-identification paradigm and found that visual impairments follow an orderly progression along the AD course. Similarly, [24] proposed the integrated cognitive assessment, a test for the identification of animal versus non-animal images, as a reliable tool for cognitive impairment screening in dementia. Alternatively, [25], and [26] found deficits in the visual processing capabilities of AD patients compared to healthy age-matched controls when they were evaluated using the rapid serial visual presentation (RSVP). In this task, the patients are required to identify two target letters separated by a number of intervening distractors which are rapidly presented on the computer screen (see Fig. 1). Trials with different number of intervening distractors are designed to evaluate the attentional and visual dynamics capabilities of the patients.

In this paper, our goal is to evaluate the feasibility of a computerized visual dynamics test for the detection of cognitive impairment in AD screening. To this end, we implemented a version of the RSVP and we conducted a preliminary study to evaluate the performance of two groups: patients (mild AD and MCI-non-AD) and healthy age-matched controls. We evaluated the performance of the participants in the RSVP in terms of the so-called attentional blink (AB) and attentional masking (AM). AB refers to the inability to recall T2 after correctly reporting T1. On the other hand, AM refers to the inability to recall T1 after correctly reporting T2. According to previous studies, healthy older adults do not show the latter effect [25, 26]. Considering this, our motivation to study this test was two-fold: (1) the RSVP assesses visual dynamics and working memory, two of the first areas affected by AD [24]; and (2), the RSVP is an auto-scored and computerized test. With this in mind, we evaluated the ability of the RSVP to discriminate the two groups studied, and we compared the results with two of the most popular brief cognitive tests used in Spain for AD screening: the CDT and the Phototest. We conducted this preliminary study in collaboration with the cognitive and behavioral neurology unit (CBNU) at Hospital Universitario Virgen de las Nieves de Granada (Spain).

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