Jaap Murre | University of Amsterdam (original) (raw)

Papers by Jaap Murre

Biological Cybernetics, 1995

We develop a mathematical formalism or calculating connectivity volumes generated by specific top... more We develop a mathematical formalism or calculating connectivity volumes generated by specific topologies with various physical packing strategies. We consider four topologies (full, random, nearest-neighbor, and modular connectivity) and three physical models: (i) interior packing, where neurons and connection fibers are intermixed, (ii) sheeted packing where neurons are located on a sheet with fibers running underneath, and (iii) exterior packing where the neurons are located at the surfaces of a cube or sphere with fibers taking up the internal volume. By extensive cross-referencing of available human neuroanatomical data we produce a consistent set of parameters for the whole brain, the cerebral cortex, and the cerebellar cortex. By comparing these inferred values with those predicted by the expressions, we draw the following general conclusions for the human brain, cortex, and cerebellum: (i) Interior packing is less efficient than exterior packing (in a sphere). (ii) Fully and randomly connected topologies are extremely inefficient. More specifically we find evidence that different topologies and physical packing strategies might be used at different scales. (iii) For the human brain at a macro-structural level, modular topologies on an exterior sphere approach the data most closely. (iv) On a mesostructural level, laminarization and columnarization are evidence of the superior efficiency of organizing the wiring as sheets. (v) Within sheets, microstructures emerge in which interior models are shown to be the most efficient. With regard to interspecies similarities and differences we conjecture (vi) that the remarkable constancy of number of neurons per underlying square millimeter of cortex may be the result of evolution minimizing interneuron distance in grey matter, and (vii) that the topologies that best fit the human brain data should not be assumed to apply to other mammals, such as the mouse for which we show that a random topology may be feasible for the cortex.

Memory, Jan 1, 2005

We investigated the age distribution of autobiographical memories with the Galton-Crovitz method ... more We investigated the age distribution of autobiographical memories with the Galton-Crovitz method through the Internet. Almost 2000 participants in the United States and the Netherlands aged between 11 and 70 years participated. They were presented with 10 cue words, and were asked to recall and date autobiographical memories. We found strong evidence for a "reminiscence bump" in all participant groups at all ages, with peaks at ages 15-18 for men and 13-14 for women. This peak could be localised more precisely than in previous studies due to our large sample size. We were able to remove the forgetting effect from the empirical age distribution with a method that allows separate estimation of memory encoding and forgetting. American participants showed a tendency to report older memories than the Dutch. Age group and level of education did not influence the lifetime encoding function.

Cognitive Neuropsychology, 2005

Memory & Cognition, 2005

A retention study is presented in which participants answered questions about news events, with a... more A retention study is presented in which participants answered questions about news events, with a retention interval that varied within participants between 1 day and 2 years. The study involved more than 14,000 participants and around 500,000 data points. The data were analyzed separately for participants who answered questions in Dutch or in English, providing an opportunity for replication. We fitted models of varying complexity to the data in order to test several hypotheses concerning retention. Evidence for an asymptote in retention was found in only one data set, and participants with greater media exposure displayed a higher degree of learning but no difference in forgetting. Thus, forgetting was independent of initial learning. Older adults were found to have forgetting curves similar to those of younger adults.

Journal of Affective Disorders, 2011

Objective: Although electroconvulsive therapy (ECT) is generally considered effective against dep... more Objective: Although electroconvulsive therapy (ECT) is generally considered effective against depression, it remains controversial because of its association with retrograde memory loss. Here, we assessed memory after ECT in circumstances most likely to yield strong retrograde amnesia. Method: A cohort of patients undergoing ECT for major depression were tested before and after ECT, and again at 3-months follow-up. Included were 21 patients scheduled to undergo bilateral ECT for severe major depression and 135 controls matched for gender, age, education, and media consumption. Two memory tests were used: a verbal learning test to assess anterograde memory function, and a remote memory test that assessed memory for news during the course of one year. Results: Before ECT the patients' scores were lower than those of controls. They were lower again after treatment, suggesting retrograde amnesia. At follow-up, however, memory for events before treatment had returned to the pre-ECT level. Memory for events in the months after treatment was as good as that of controls. Limitations: The sample size in this study was not large. Moreover, memory impairment did not correlate with level of depression, which may be due to restriction of range. Conclusions: Our results are consistent with the possibility that ECT as currently practiced does not cause significant lasting retrograde amnesia, but that amnesia is mostly temporary and related to the period of impairment immediately following ECT.

European Journal of Cognitive Psychology, 2010

Many tests of retrograde amnesia consist of questions on news events. It is therefore important t... more Many tests of retrograde amnesia consist of questions on news events. It is therefore important to know how such questions are answered by normal adults. We analysed the retention of news events in a sample of 12,913 participants, who provided basic demographic information and subsequently answered questions about news events randomly sampled from a database. We investigated whether demographic variables could predict differences in the intake and retention of news from several categories, such as sports and business news. Although demographic variables did affect general performance on news questions, differential effects on specific categories were marginal. Gender influenced performance on questions about business news, both age and educational attainment affected performance on political news, and educational attainment also had an effect on performance on science news.

Acta Psychologica, 2013

Over 100,000 verbal and visuospatial immediate and delayed memory tests were presented via the In... more Over 100,000 verbal and visuospatial immediate and delayed memory tests were presented via the Internet to over 28,000 participants in the age range of 11 to 80. Structural equation modeling pointed to the verbal versus visuospatial dimension as an important factor in individual differences, but not the immediate versus delayed dimension. We found a linear decrease of 1% to 3% per year in overall memory performance past the age of 25. For visuospatial tests, this decrease started at age 18 and was twice as fast as the decrease of verbal memory. There were strong effects of education, with the highest educated group sometimes scoring one full standard deviation above the lowest educated group. Gender effects were small but as expected: women outperformed men on the verbal memory tasks; men outperformed women on the visuospatial tasks. We also found evidence of increasing proneness to false memory with age. Memory for recent news events did not show a decrease with age.

Archives of General Psychiatry, 2005

Episodic memory impairments are well characterized in schizophrenia, but their neural origin is u... more Episodic memory impairments are well characterized in schizophrenia, but their neural origin is unclear. To determine whether the episodic memory impairments in schizophrenia may originate from reduced parahippocampal connectivity. Experimental in silico model. Department of Psychology, University of Amsterdam, Amsterdam, the Netherlands. A new, in silico medial temporal lobe model that simulates normal performance on a variety of episodic memory tasks was devised. The effects of reducing parahippocampal connectivity in the model (from perirhinal and parahippocampal cortex to entorhinal cortex and from entorhinal cortex to hippocampus) were evaluated and compared with findings in schizophrenic patients. Alternative in silico neuropathologies, increased noise and loss of hippocampal neurons, were also evaluated. In the model, parahippocampal processing subserves integration of different cortical inputs to the hippocampus and feature extraction during recall. Reduced connectivity in this area resulted in a pattern of deficits that closely mimicked the impairments in schizophrenia, including a mild recognition impairment and a more severe impairment in free recall. Furthermore, the schizophrenic model was not differentially sensitive to interference, also consistent with behavioral data. Notably, neither increased noise levels nor a reduction of hippocampal nodes in the model reproduced this characteristic memory profile. Taken together, these findings highlight the importance of parahippocampal neuropathology in schizophrenia, demonstrating that reduced connectivity in this region may underlie episodic memory problems associated with the disorder.

Psychological Bulletin, 2004

Memory loss in retrograde amnesia has long been held to be larger for recent periods than for rem... more Memory loss in retrograde amnesia has long been held to be larger for recent periods than for remote periods, a pattern usually referred to as the Ribot gradient. One explanation for this gradient is consolidation of long-term memories. Several computational models of such a process have been presented, and have shown how consolidation can explain characteristics of amnesia, effects of arousal on memory, and episodic memory in semantic dementia. These models have not elucidated how consolidation must be envisaged; it remains a largely hypothetical process. Here findings are reviewed that shed light on how consolidation may be implemented in the brain. Moreover, evidence is weighed that supports its existence, or supports one of its competitors as explanations of the Ribot gradient: that it results from only partial damage to the hippocampal memory system (as stated by multiple trace theory), or that it result from a sparing of semanticized memories. Consolidation theory, multiple trace theory and semantization can all handle some findings well, and others not. Conclusive evidence for or against consolidation thus remains to be found.

Philosophical Psychology, 2007

Hippocampus, 2004

It has been suggested that hippocampal mode shifting between a storage and a retrieval state migh... more It has been suggested that hippocampal mode shifting between a storage and a retrieval state might be under the control of acetylcholine (ACh) levels, as set by an autoregulatory hippocampo-septohippocampal loop. The present study investigates how such a mechanism might operate in a large-scale connectionist model of this circuitry that takes into account the major hippocampal subdivisions, oscillatory population dynamics and the time scale on which ACh exerts its effects in the hippocampus. The model assumes that hippocampal mode shifting is regulated by a novelty signal generated in the hippocampus. The simulations suggest that this signal originates in the dentate. Novel patterns presented to this structure lead to brief periods of depressed firing in the hippocampal circuitry. During these periods, an inhibitory influence of the hippocampus on the septum is lifted, leading to increased firing of cholinergic neurons. The resulting increase in ACh release in the hippocampus produces network dynamics that favor learning over retrieval. Resumption of activity in the hippocampus leads to the reinstatement of inhibition. Despite theta-locked rhythmic firing of ACh neurons in the septum, ACh modulation in the model fluctuates smoothly on a time scale of seconds. It is shown that this is compatible with the time scale on which memory processes take place. A number of strong predictions regarding memory function are derived from the model.

Frontiers in Psychology, 2013

We describe a mathematical model of learning and memory and apply it to the dynamics of forgettin... more We describe a mathematical model of learning and memory and apply it to the dynamics of forgetting and amnesia. The model is based on the hypothesis that the neural systems involved in memory at different time scales share two fundamental properties: (1) representations in a store decline in strength (2) while trying to induce new representations in higher-level more permanent stores. This paper addresses several types of experimental and clinical phenomena: (i) the temporal gradient of retrograde amnesia (Ribot's Law), (ii) forgetting curves with and without anterograde amnesia, and (iii) learning and forgetting curves with impaired cortical plasticity. Results are in the form of closed-form expressions that are applied to studies with mice, rats, and monkeys. In order to analyze human data in a quantitative manner, we also derive a relative measure of retrograde amnesia that removes the effects of non-equal item difficulty for different time periods commonly found with clinical retrograde amnesia tests. Using these analytical tools, we review studies of temporal gradients in the memory of patients with Korsakoff's Disease, Alzheimer's Dementia, Huntington's Disease, and other disorders.

Neurocomputing, 2002

Episodic memory impairment is one of the most reliable neuropsychological ÿndings in schizophreni... more Episodic memory impairment is one of the most reliable neuropsychological ÿndings in schizophrenia. It has been suggested that medial temporal lobe abnormalities in schizophrenia underlie this impairment. We suggest that the speciÿc memory deÿcits in schizophrenia may be caused by abnormal hippocampo-cortical communication via parahippocampal areas. We have used connectionist simulations to investigate this notion. The simulations involve list learning in a model that incorporates characteristics of the hippocampal and parahippocampal region. In this model context is used to store and recall episodic memories. Reduction of the nodes in the parahippocampal module of the model resulted in a schizophrenia-like memory deÿcit proÿle. (J.M.J. Murre), talamini@psy.uva.nl (L.M. Talamini). 0925-2312/02/$ -see front matter c 2002 Published by Elsevier Science B.V. PII: S 0 9 2 5 -2 3 1 2 ( 0 2 ) 0 0 4 9 3 -9

Frontiers in Human Neuroscience, 2014

Journal of Visualized Experiments, 2014

Physica A: Statistical Mechanics and its Applications, 2004