Spike-timing dependent plasticity in a transistor-selected resistive switching memory.

In a neural network, neuron computation is achieved through the summation of input signals fed by synaptic connections. The synaptic activity (weight) is dictated by the synchronous firing of neurons, inducing potentiation/depression of the synaptic connection. This learning function can be supported by the resistive switching memory (RRAM), which changes its resistance depending on the amplitude, the pulse width and the bias polarity of the applied signal. This work shows a new synapse circuit comprising a MOS transistor as a selector and a RRAM as a variable resistance, displaying spike-timing dependent plasticity (STDP) similar to the one originally experienced in biological neural networks. We demonstrate long-term potentiation and long-term depression by simulations with an analytical model of resistive switching. Finally, the experimental demonstration of the new STDP scheme is presented.

Cognitive profile in spastic paraplegia with thin corpus callosum and mutations in SPG11.

Autosomal recessive hereditary spastic paraplegia with thinning of the anterior corpus callosum (ARHSP-TCC) due to mutations in SPG11 on chromosome 15q (MIM610844) is the single most common cause of ARHSP. It is characterized by slowly progressive paraparesis and peripheral neuropathy. Although cognitive impairment, sometimes diagnosed as mental retardation, is an almost invariable feature, the extent and specific neuropsychological features are not fully understood. We report a comprehensive neuropsychological assessment in two ARHSP-TCC patients harbouring mutations in SPG11. A specific impairment in executive functions occurring even before cognitive decline, may be considered the core of the neuropsychological profile of patients harbouring mutations in SPG11.