53 According to the authors, these results suggest that attention and memory, which are impaired in schizophrenic patients and involved in the rePD98059 mouse production task, are confounding factors in schizophrenia. Moreover, dopamine dysregulation is involved in both schizophrenia and cognition. Further studies are necessary to clarify how time estimation impairments in psychiatric patients are related to biochemical changes and to cognitive deficits. Discussion Our work is the first to compare time judgments obtained in several groups of Inhibitors,research,lifescience,medical patients with different neurological

disorders using the same time estimation paradigm (ie, reproduction and production of three time durations in seconds). We can deduct from this the memory systems and the brain structures involved in each time estimation task (Table I). TABLE I. The involvement of the memory systems and the associated brain structures in Inhibitors,research,lifescience,medical the reproduction and production of short (5 seconds) and long durations (14 and 38 seconds). Short-term memory Short-term and working memory would be involved in both reproductions and productions of durations in the second range. The accurate reproduction of short durations by the amnesic patients is due to the fact that short-term memory is preserved. Inversely, TBI and PD patients, who generally show working memory deficits, made respectively more Inhibitors,research,lifescience,medical variable duration

reproductions and productions, Inhibitors,research,lifescience,medical and inaccurate productions. The frontal lobe would be necessary to maintain attention during the trial while accumulating temporal information in working memory. Long-term memory This would be differently involved in the productions and reproductions of durations in the second range. In the reproduction task, episodic memory would be necessary to reproduce durations exceeding 10 to 15 seconds. The delay introduced between Inhibitors,research,lifescience,medical the encoding and the reproduction

phases would require a retrieval of information from long-term memory when the target durations exceed the short-term memory span. In AC, the underestimation of long durations reflects a defective retrieval of information in episodic Adenylyl cyclase memory consecutive to bilateral medial temporal lesions. A long-term memory system would also be required in the production task. When subjects have to produce a target duration given in conventional units of time, they must compare the content of time units accumulated and stored in working memory with a representation of time stored in a “reference memory.”5 Since the amnesic patient was able to produce durations as normal controls, we propose that this reference memory could be a semantic memory, which is preserved in AC. The representation of time would be stored with the general knowledge of the world in semantic memory. We would know what a second signifies, just as we know who is the president of the United States.