Physics Letters A 313 (2003) 158–161 www.elsevier.com/locate/pla Short-term memory and critical clusterization in brain neurons spike series A. Bershadskii a,∗ , E. Dremencov b , G. Yadid b a ICAR, PO Box 31155, Jerusalem 91000, Israel b Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel Received 31 March 2003; accepted 17 April 2003 Communicated by V.M. Agranovich Abstract A new phenomenon: critical clusterization, is observed in the neuron firing of a genetically defined rat model of depression. The critical clusterization is studied using a multiscaling analysis of the data obtained from the neurons belonging to the Red Nucleus area of the depressive brains. It is suggested that this critical phenomenon can be partially responsible for the observed ill behavior of the depressive brains: loss of short-term motor memory and slow motor reaction.  2003 Elsevier Science B.V. All rights reserved. PACS: 87.19.La; 87.17.-d; 64.60.Fr 1. Introduction Underlying physics (kinetics) of the neuron firing is actively studied in the recent years (see, for in- stance, [1–12]). In papers [9,12] we studied probabilis- tic properties of spiking time-series generated by neu- rons belonging to the Red Nucleus area of brain. The Red Nucleus is a prominent structure within the ros- tral midbrain. Very little is known about the functions of the Red Nucleus in humans. Inputs to the Red Nu- cleus arise from motor areas of the brain and in partic- ular the deep cerebellar nuclei and the motor cortex. It is known that humans with deep depression have in- trinsic locomotor’s problems. Therefore, investigation * Corresponding author. E-mail address: ark2@eudoramail.com (A. Bershadskii). of Red Nucleus for genetically defined rat models of depression can be useful for understanding the mental disorder origin. Our electrophysiological experiment in vivo was performed with a genetically defined rat model of de- pression: Flinders Sensitive Rat Line (FSL). Animals were anaesthetized and mounted in stereotaxic appa- ratus. The hole was drilled 4.2 mm anterior from the interaural line and 1.0 mm lateral from the medial line. Extracellular recordings were processed by an elec- trode from Red Nucleus. Each recording from the sin- gle cell included about 2000 spike events. It is shown in [9] that on the level of individual spikes the FSL Red Nucleus neurons have no pos- sibility for an intelligent communication with their environment due to an uniform probability distribu- tion of their membrane threshold values. There ex- ists a possibility that an average value of the mem- 0375-9601/03/$ – see front matter  2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0375-9601(03)00718-7