A hybrid neuro-electronic interface is a cell-cultured micro electrode array, acting as a neural information transducer for stimulation and/or recording of neural activity in the brain or the spinal cord (ventral motor region or dorsal sensory region). It consists of an array of micro electrodes on a planar substrate, the electrodes being covered by a network of cultured neurons. The cultured neuron network layer acts as a natural host for in vivo neural connections. Besides this function, live neural networks can become spontaneously active and have the capability of information processing, as 'minibrains'. One may envisage future applications of these intermediary networks as 'front-end' signal processors. The paper presents results on spatio-temporal activity patterns and their characterization in neural networks, cultured from dissociated rat visual cortex. Cultures lasted 43 days in vitro on multi electrode plates with 60 electrode sites and started activity after about seven days. Firing rates increase with time thereafter. Typical 'pacemaker'-and-burst firing patterns are seen, the time characteristics of which change over days, typically.