Animals Article Avoidance Learning Cerebral Cortex Hippocampus Humans N-Methylaspartate Receptors, N-Methyl-D-Aspartate abdominal pain animal animal experiment anticipatory nausea and vomiting avoidance behavior brain cortex brain region conditioned place avoidance controlled study dorsal hippocampus enzyme activity hippocampus human lithium chloride male memory consolidation metabolism n methyl dextro aspartic acid n methyl dextro aspartic acid receptor n methylaspartic acid nonhuman place preference