Under anaesthesia or in deep sleep, different parts of the brain have a distinctive slow oscillatory activity, characterised by states of high membrane potential and intensive spiking activity, the Up-states; followed by hyperpolarisation and quiescence, the Down-states. This activity has been previously described in vitro and in vivo in the cortex and the striatum, across several species. Here, we look into it, during anaesthesia, in the mouse brain. Using whole-cell patch-clamp recordings of cortical cells, it was possible to compare different signal processing methods used to extract the Up-and- Down states in extracellular recordings of the cortex. Our results show that the method based on the Multi-Unit Activity (&gt; 200Hz) have better ac- curacy than High-Gamma Range (20 100Hz) or wavelet decomposition (&lt; 2Hz band). After establishing the most robust method, this was used to compare the intracellular recordings of striatal cells to different parts of the cortex. The results obtained here support a functional connection between the dorsolateral striatal neurons and the ipsilateral barrel field. They also support a functional connection between dorsomedial striatal cells and the primary visual cortex. The analysis of delay between recordings allowed to establish temporal relationships between the contralateral barrel field, the ipsilateral barrel field, and the dorsolateral striatum; and between the ipsilateral barrel field, the ipsilateral primary visual field and the dorsomedial striatum. / <p>External Advisor: Dr. Ramon Reig, from Karolinska Institutet</p>