Animal studies provided evidence that stress modulates multiple memory systems, favoring caudate nucleus-based "habit" memory over hippocampus-based "cognitive" memory. However, effects of stress on learning strategy and memory consolidation were not differentiated. We specifically address the effects of psychosocial stress on the applied learning strategy in humans. We designed a spatial learning task that allowed differentiating spatial from stimulus-response learning strategies during acquisition. In 13 subsequent trials, participants (88 male and female students) had to locate a "win" card out of four placed at a fixed location in a 3D model of a room. Relocating one cue in the last trial allowed inferring the applied learning strategy. Half of them participated first in the "Trier Social Stress Test." Salivary cortisol and heart rate measurements were taken. Stressed participants used a stimulus-response strategy significantly more often than controls. Subsequent verbal report revealed that spatial learners had a more complete awareness of response options than stimulus-response learners. Importantly, learning performance was not affected by stress. Taken together, stress prior to learning facilitated simple stimulus-response learning strategies in humans-at the expense of a more cognitive learning strategy. Depending on the context, we consider this as an adaptive response.

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This translational comparison demonstrates a cross-species consistency in pharmacological effect and elucidates ketamine-induced alterations in PFC-HC coupling, a phenotype often disrupted in pathological conditions, which may give clue to understanding of psychiatric disorders and their onset, and help in the development of new treatments.

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Memory is facilitated when the retrieval context resembles the learning context. The brain structures underlying contextual influences on memory are susceptible to stress. Whether stress interferes with context-dependent memory is still unknown. We exposed healthy adults to stress or a control procedure before they learned an object-location task in a room scented with vanilla. Memory was tested 24 h later, either in the same or in a different context (unfamiliar room without the odor). Stress administered prior to encoding abolished the context-dependent memory enhancement found in the control group. Thus, these findings represent the first demonstration of impaired context-dependent memory following stress.

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Previous research has accumulated convincing evidence to show that the human cerebellum contributes to the short-term storage of verbal information, but its specific role in brain networks involved in phonological storage remains uncertain. In a randomized, crossover and sham-controlled design, we here combined transcranial direct current stimulation (tDCS), applied to the right cerebellum, with fMRI to investigate systematically the contribution of the human cerebellum to encoding, maintenance, and retrieval of verbal information. After anodal, but not cathodal, tDCS, we found a reduced item recognition capacity together with an attenuated neural signal from the right cerebellar lobule VIIb, specifically during the late encoding phase. Within this phase, tDCS furthermore affected task-associated functional connections between right cerebellar lobule VIIb and the posterior parietal cortex. These findings suggest that the right cerebellar lobule VIIb interacts with the posterior parietal cortex, specifically during the late stages of verbal encoding, when verbal information enters phonological storage.

Depression is a common disorder in the elderly handicapping patients with affective and cognitive symptoms. Because of their good tolerability relative to the older tricyclic compounds, selective serotonin reuptake inhibitors (SSRIs) are increasingly used for the treatment of depression in the elderly. Little is known about their effects on cognition in elderly patients. In the present 4-wk, single-centre, randomized, open-label trial we investigated the antidepressive effects of escitalopram, an SSRI, in 18 elderly depressed patients [mean age (+/-s.e.m.) 76.2+/-1.8 yr] compared to 22 healthy age-matched controls (mean age 76.9+/-1.8 yr). Affective and cognitive symptoms were assessed using the Geriatric Depression Scale (GDS), Mini-Mental State Examination (MMSE), and a face portrait recognition test to assess memory for happy and angry faces. Depressed patients prior to treatment had markedly reduced memory performance. Treatment with escitalopram improved affective and cognitive symptoms significantly. Furthermore, escitalopram treatment improved memory for negative facial stimuli. Control subjects confirmed the well- established memory bias favouring recognition of identities acquired with happy expressions. Importantly, this bias was absent in depressed patients prior to, but also after treatment. In conclusion, escitalopram, even after a relatively short treatment period, was effective in treating depression in the elderly and may help improve cognitive performance for social stimuli.