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Associating stimuli with positive or negative reinforcement is essential for survival, but a complete wiring diagram of a higher-order circuit supporting associative memory has not been previously available. Here we reconstruct one such circuit at synaptic resolution, the Drosophila larval mushroom body. We find that most Kenyon cells integrate random combinations of inputs but that a subset receives stereotyped inputs from single projection neurons. This organization maximizes performance of a model output neuron on a stimulus discrimination task. We also report a novel canonical circuit in each mushroom body compartment with previously unidentified connections: reciprocal Kenyon cell to modulatory neuron connections, modulatory neuron to output neuron connections, and a surprisingly high number of recurrent connections between Kenyon cells. Stereotyped connections found between output neurons could enhance the selection of learned behaviours. The complete circuit map of the mushroom body should guide future functional studies of this learning and memory centre., Author(s): Katharina Eichler [1, 2]; Feng Li [1]; Ashok Litwin-Kumar [3]; Youngser Park [4]; Ingrid Andrade [1]; Casey M. Schneider-Mizell [1]; Timo Saumweber [5]; Annina Huser [2]; Claire Eschbach [1]; [...]

'Learning by doing' promises to lead to more efficient acquisition than other learning strategies. Indeed, much research has established that enactment leads to better recognition and recall of simple verb-object phrases (e.g., 'light the match', 'touch your nose') than intentional learning without enactment. Only few studies have compared the acquisition of novel naturalistic activities (e.g., 'to fold a paper frog') across different study conditions, and only a few different activities have been investigated overall. Two experiments tested whether five very different such activities can be carried out better after enactment learning than after observing a model or after pictorial learning instructions. No evidence of different performance across study conditions was obtained. Keywords: Enactment, observation, pictorial learning, action sequences, novel naturalistic activities, memory recall, performance recall, Every day, people perform naturalistic activities that consist of well-known goal-oriented action sequences, such as making coffee, preparing cookie dough, or changing a light bulb. Occasionally, people also need to [...]

Summation tests were used to assess whether participants in a human predictive judgement task learned that some cues (foods) prevented the occurrence of the outcome (migraine). In three experiments the preventative effect of a conditioned inhibitor, I, trained in the design, P+, PI-, I-, was stronger than that of a negative control cue, N, that had been presented alone with the same frequency and simply predicted no outcome. This control cue, N, also passed the summation test when compared to a novel control cue. Experiments 2 and 3 examined whether the latter negative control effect was attributable to differential inhibition. Manipulations designed to alter context learning and the magnitude of the negative contingency did not affect the properties of the negative control cue. Thus, these experiments did not support the possibility that a cue given simple negative training acquires differential inhibition. Regardless of the mechanism underlying the negative control effect, the consistent finding that the conditioned inhibition cue, I, reduced prediction of the outcome more than did the negative control cue, N, provides evidence for true conditioned inhibition whose acquisition requires co-occurrence of the preventative cue with a positive training cue.

The influence of a secondary task on forward blocking of human contingency ratings was examined. A smaller blocking effect was found when participants performed a highly demanding secondary task than when they performed a less demanding secondary task. The modulatory effect of secondary task difficulty was significant only when the secondary task was administered during both the learning and the test phase of the contingency judgement task. The results suggest that forward blocking in human contingency learning cannot be fully accounted for by associative processes. Instead, forward blocking seems to depend at least partially on deliberate deductive reasoning processes.