Figure 4
From: Early hippocampal volume loss as a marker of eventual memory deficits caused by repeated stress
Performance in the Morris Water-Maze task halfway through chronic stress.
(a,b) Protocol for the Morris water maze task. (a) Protocol for trials in each session. Each session consisted of five trials with an inter-trial interval of 30 seconds. The difference in the path length of the first and the last trial of a session (green dotted line with arrow) was called the path length difference within a session. (b) The same protocol was repeated in session1, session2 and session3 over day4, day5 and day6 respectively. The sum of the differences of the path length in the last trial on day4 and first trial on day5 and the last trial on day5 and the first trial on day6 (blue dotted line with arrow) was called the path length difference between sessions. (c) Escape latency in sec (mean ± SEM) for all trials across the three sessions. By the end of the task, both the stressed and unstressed groups of animals acquire spatial memory of the location of the platform. The stressed (N = 9) group shows significantly higher escape latency than unstressed (N = 10) group only during the first trial on session 2 (Factor stress: F(1, 17) = 0.07067, p = 0.7936; factor trials: F(4, 68) = 5.116, p = 0.0012; interaction: F(4, 68) = 4.289, p = 0.0037; post hoc Fischer’s LSD test). (d) Path length difference within session for the three sessions (mean ± SEM). It is significantly different between stressed and unstressed group of animals and across sessions (Factor stress: F(1, 17) = 6.095, p = 0.0245; factor sessions: F(2, 34) = 3.542, p = 0.0400; interaction: F(2, 34) = 2.249, p = 0.1209). The stressed (N = 9) group shows significantly higher path length difference within session than the unstressed (N = 10) group in session2 (post hoc Sidak’s multiple comparison test). (e) Path length difference between sessions (mean ± SEM). The stressed (N = 9) group has a significantly more negative path length difference between sessions as compared to the unstressed (N = 10) group (Unpaired t-test: p = 0.042). (f) Swim velocity for all the trials across the three sessions (mean ± SEM) do not vary for the stressed and unstressed animals. (c–e) An asterisk indicates significant differences (*p < 0.05 level).
