Acute effects of alcohol on neural correlates of episodic memory encoding

1. Acute effects of alcohol on neural correlates of episodic memory encoding Söderlund, H., Grady, C.L., Easdon, C. & Tulving, E. By Miranda Marchand

2. Introduction • The effects of alcohol on on episodic memory have been well established through laboratory memory tasks • It has been found that encoding of memories is more affected than retrieval • Previous studies have shown that: • When compared to a placebo, alcohol reduces cerebral blood flow in task-implicated areas during perceptual processing, simulated driving, verbal fluency and divided attention (Calhoun et al., 2004, Haier et al., 1999, Wendt and Risberg, 2001) • Though alcohols effects have been demonstrated through behaviour, no previous studies have identified the neural relations of memory impairment due to alcohol consumption • Hypothesized that alcohol would impair memory performance, particularly associative memory due to its effects on the hippocampus

3. Participants • 27 males • Prescreened for any neurological, psychiatric or medical disorders • Those on any medication, who were left-handed, had not spoken English since age 7 and were outside the 20-40 year range, were using marijuana on a regular basis or had problematic drinking habits were excluded • Accepted participants consumed between 2 and 16 drinks a week • No one had drink a on more than 3 separate occasion during a week • Experimental and control groups were matched for age, education and initial memory performance

4. Procedure • Participants were seen on 2 days • Day 1 • Participants were given practice trials of the different tasks that would be performed in the scanner • Participants were then given their drinks – either placebo or alcohol • Participants were placed in the scanner to complete the tasks – this took about an hour • Day 2 • Participants returned the next day to test their memory for materials presented • There was no beverage or scanning in the second day

5. Experiments

6. Experiments – Object Pairs • Experimental condition • 18 pairs of line drawings of objects were presented in the experimental condition, each pair was presented twice, each block contained 6 pairs • Each pair was presented for 4 seconds, and then a cross-hair was presented for 1 second • Participants were asked to decide if there was a meaningful relationship • Control condition • Pairs of the same line drawing were presented in 5 blocks, 3 pairs per block, 15s long • Participants had to indicate which of the drawings was smaller

7. Experiments – Face-Name Pairs • Experimental condition • Participants were shown photos of people with a gender appropriate name and were asked to judge whether the name fit the face • Shown 5 per block, each pair was shown for 4 seconds followed by a 1 second cross hair • Control condition • Participants were shown photos labeled either man or woman and they had to determine whether the label was correct or not • Shown 3 pairs per block and there was a total of 7 blocks

8. Results – Object Pair fMRI Data • The only region active during both associative and perceptual encoding was an area in the left superior frontal gyrus • Regions activated in the placebo group • Frontal • Cerebellum • Parahippocampalgyrus • Occipital cortex • Precuneus • Regions activated in the alcohol group • Medial frontal gyrus

9. Results –Face-Name fMRI Data • Main difference between the alcohol and placebo groups was the activation of the right frontal area in the placebo group • The left precuneus and and right temporal regions were deactivated in the placebo group, no change in activation was seen in the alcohol group

11. Results – Comparing BOLD responses • Hippocampus: • Alcohol group showed activation during both conditions • Placebo group only showed activation during the semantic condition

12. Analysis – Semantic Encoding • What area was activated during all semantic encoding? • Placebo group – the left inferior-middle frontal gyrus was activated during all semantic encoding • Alcohol group – this prefrontal activation was seen only during the encoding of verbal materials

13. The Three Major Findings • When performance was not significantly effected by alcohol the group activated the same prefrontal regions as the placebo group • Encoding under the influence of alcohol was associated with reduced activity in other encoding related areas • The apparent lack of parahippocampal/fusiform activity in the alcohol group was actually due to non-specific activation during both experimental and control conditions

14. My Thoughts on the Paper • Supported behavioural experiment findings with the use of fMRI • Was very well laid out • The majority of the paper was easy to understand • There were a lot of experiments presented in paper • The “control” condition was not only used on the control group, made understanding the experiments more complicated • Limitations: Only used males • Future experiments: use females

15. Questions?

16. References • Calhoun, V.D., Pekar, J.J., Pearlson, G.D. (2004). Alcohol intoxicationeffectson simulated driving: exploring alcohol-dose effects on brain activation using functional MRI. Neuropsychopharmacology29, 2097–2107. • Haier, R.J., Schandler, S.L., MacLachlan, A., Soderling, E., Buchsbaum, M.S., Cohen, M.J., (1999). Alcohol induced changes in regional cerebral glucose metabolic rate during divided attention. Pers. Individ. Dif. 26, 425–439. • Söderlund, H., Grady, C.L., Easdon, C. & Tulving, E.(2006). Acute effects of alcohol on neural correlates of episodic memory encoding. Neuroimage, 35, 928-939. • Wendt, P.E., Risberg, J., (2001). Ethanol reduces rCFB activation of left dorsolateral prefrontal cortex during a verbal fluency task. Brain Lang. 77, 197–215.