EPISODIC MEMORY DEFICITS: COMPARISON BETWEEN PERSONS WITH DEMENTIA OF ALZHEIMER’S TYPE, MILD COGNITIVE IMPAIRMENT & HEALTHY ELDERLY INDIVIDUALS

Reuben Thomas Varghese 1 and S.P. Goswami 2 . 1. Scientist B, Department of SpeechLanguage Sciences All India Institute of Speech & Hearing, Mysuru, India. 2. Prof. in Speech Pathology, Department of Speech – Language Pathology All India Institute of Speech & Hearing, Mysuru, India. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History Received: 06 July 2018 Final Accepted: 08 August 2018 Published: September 2018


ISSN: 2320-5407
Int. J. Adv. Res. 6(9), 300-306 301 Alzheimer's Disease. Deficits in memory has received the most attention in aging population (Grady, 2008;Park & Gutchess, 2002). Episodic memory refers to the ability for recollecting an autobiographical memory of events that occurred in a particular temporal and spatial context (Squire, 2004). The most important characteristic of episodic memory is autonoetic awareness. This helps an individual capable of movement at will in subjective time, by remembering past experiences, or imagining possible future experiences (Wheeler & Buckner, 2004).Numerous studies have reported age-related changes in episodic memory in healthy individuals (Budson and Price, 2005;Kamath & Prema, 2001), persons with MCI ( Irish et.al, 2001) and persons with Dementia (Sunil & Shyamala 2009;Anjana & Shanbal, 2010).The studies revealed that episodic memory scores deficits were more in dementia group and MCI group compared to the healthy elderly individuals. It was also noticed that memory deficits tend to increase with age. The temporal lobe, which comprises of the hippocampus, and the prefrontal cortex are key to episodic memory. Studies have reported that the hippocampus is one of the first brain structures damaged in both persons with Dementia of Alzheimer's type and Mild Cognitive Impairment (Zhan et al, 2016)

Method:-
The research design taken for the present study was standard group comparison. A total of sixty participants were recruited for the present study. These participants were categorized under three subgroups, namely group I, group II and group III. The participants included in group I were twenty normal healthy controls (NHC), participants in group II were twenty persons with Mild Cognitive Impairment (MCI) and participants in group III were twenty persons with Mild Dementia of Alzheimer's type (DAT). All the three participant groups were again sub divided into three age-groups [(>60-65yrs, >65-70 yrs & >70-75 yrs)]. The participants in group II and group III were identified through local hospitals, dementia support groups and dementia clinics in Mysuru city, Karnataka, India The selection criteria common for all the groups were as follows: 1. They were above the age of 60 years 2. They were native Kannada speakers with adequate hearing and vision (corrected). For hearing screening, Lings six sound test and for vision Zeiss Online vision Screening Test was considered. 3. The opinion of the neurologist/ psychiatrist was considered for participant selection. 4. All participants were evaluated for their mental status on Mini Mental State Examination (Folstein, Folstein & McHugh, 1975) and those who failed below a score of 23 were taken for group II and group III and participants who had passed a score of 23 and above (indicates no cognitive impairment) were taken for the Group I.

Selection Criteria specific for Group I:-
Participants with no history of hoarse voice, major neurological or psychiatric illness or of alcoholism or drug abuse were included.

Selection criteria specific for Group II:-
The opinion of the neurologist/ psychiatrist according to MoCA-Montreal Cognitive Assessment Scale (Nasreddine, Bédirian, Charbonneau, Whitehead, Collin, Cummings & Chertkow, 2005) and Peterson criteria was considered for selecting MCI group.

Selection criteria specific for Group III:-
The opinion of the neurologist/ psychiatrist according to NINCDS-ADRDA (National Institute of Neurological Disorders-Alzheimer's Disease and Related Disorders Association, 2007) was taken for selecting DAT group.

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The study was carried out after the approval of the AIISH ethical committee and adhered to the ethical guidelines stated by AIISH, Mysore. Karnataka, India. Informed consent was taken from the participant / caregiver for the recording.

Material:-
Cognitive-Linguistic Assessment Protocol (CLAP, Kamath, 2001) is a test which assesses the cognitive and linguistic abilities in both young and elderly population. This test assess attention, perception & discrimination, memory, problem solving and organization.

Procedure
Each participant was seated in a noise free room. Episodic memory tasks were evaluated by using Orientation and recent memory test from the memory domain of Cognitive-Linguistic Assessment Protocol to the participants. The task was evaluated by asking questions to the participant with respect to orientation like place, time, self and a few questions pertaining to general knowledge and recent memory. The participant had to answer a total of 10 questions and 1 mark was given for each correct answer. The maximum total score for the test was 10.

Statistical Analysis
The raw scores were tabulated and subjected to statistical analysis. Shapiro Wilks test of normality was carried out.
As the data was not following assumptions of normality at 0.05 level of significance, non parametric test Kruskal-Wallis test was carried out to see the significant difference between participant groups and age groups. Further, Mann Whitney test was carried out to find pair-wise significant difference between age-groups and participant groups (HC , MCI & DAT). These analyses were carried using SPSS 21 version.

Results:-
The aim of the present study was to compare the episodic memory deficits across three age groups-group I (>60-65yrs), group II (>65-70yrs) and group III (>70-75yrs) between Persons with Dementia of Alzheimer's type (DAT), Mild Cognitive Impairment (MCI) and normal healthy controls (HC) using Cognitive-Linguistic Assessment Protocol (CLAP). Episodic memory tasks were evaluated by using orientation and recent memory test from the memory domain of Cognitive-Linguistic Assessment Protocol to the participants. The task was evaluated by asking questions to the participant with respect to orientation like place, time, self and a few questions pertaining to general knowledge and recent memory. The participant had to answer a total of 10 questions and 1 mark was given for each correct answer. The maximum total score for the test was 10.

Episodic memory deficits in NHC across age-groups
It was noticed that the mean score for NHC for episodic memory task for age group I was 9.91, age group II was 9.82 and age group III was 9.41. The overall mean score for all the age groups were 9.76. Kruskal -Wallis test revealed that there is a significant difference among different age groups for healthy controls (χ 2 (2)

Discussion:-
The study was undertaken to compare the episodic memory deficits across three age ranges (60-65yrs, 65-

Comparison between the groups
Since the standard deviation is very small, the mean scores was used as it provided a good representation. Thus from the results, we can infer that for age group I (>60-65yrs), the difference in mean scores between NHC and MCI was 0.9.The difference in mean scores between MCI and DAT was 1.69. The difference in mean scores between NHC and DAT was 2.60. For age group II (>65-70), the difference in mean scores between NHC and MCI was 1.4. The difference in mean scores between MCI and DAT was 2.22. The difference in mean scores between NHC and DAT was 3.62. For age group III (>70-75), the difference in mean scores between NHC and MCI was 1.77.The difference in mean scores between MCI and DAT was 3.42. The difference in mean scores between NHC and DAT was 5.19.Thus we can infer that as age increased, the episodic memory deficits between each participant group also increased, being more prominent for the DAT group. The decrease in the episodic memory might be due to the reduction in hippocampal and entorhinal cortex volumes in groups which might have also been affected by age advancement.

Summary & Conclusion:-
The above study was an attempt to investigate the episodic memory deficits between normal healthy controls (NHC), Persons with Mild Cognitive Impairment (MCI) and Persons with Dementia of Alzheimer's type (DAT) using memory domain of Cognitive-Linguistic Assessment Protocol (CLAP). The results of the study revealed that 305 persons with DAT exhibited more episodic memory deficits compared to MCI & NHC .This study also throws also light on early cognitive markers which can help in the differential diagnosis among all the groups. The above study also gives out red flags in terms of cognitive measures for MCI individuals which can help clinicians to plan out strategies to prevent cognitive slowing. Further research with more number of samples is warranted.