Ultra-sparse connectivity within the lateral hypothalamus

The lateral hypothalamus (LH) contains neuronal populations which generate fundamental behavioural actions such as feeding, sleep, movement, attack and evasion. Their activity is also correlated with various appetitive and consummatory behaviours as well as reward seeking. It is unknown how neural activity within and among these populations is coordinated. One hypothesis postulates that they communicate using inhibitory and excitatory synapses, forming local microcircuits. We inspected this hypothesis using quadruple whole cell recordings and optogenetics to screen thousands of potential connections in brain slices. In contrast to the neocortex, we found near zero connectivity within the LH. In line with its ultra-sparse intrinsic connectivity, we found that the LH does not generate local beta and gamma oscillations. This suggests that LH neurons integrate incoming input within individual neurons rather than through local network interactions, and that input from other brain structures is decisive for selecting active populations in LH.