http://www.ncbi.nlm.nih.gov/pubmed/24598528 QUOTE J Neurophysiol. 2014 Mar 5. [Epub ahead of print] Emerging feed-forward inhibition allows the robust formation of direction selectivity in the developing ferret visual cortex. Van Hooser SD1, Escobar GM, Maffei A, Miller P. Author information Abstract The computation of direction selectivity requires that a cell respond to joint spatial and temporal characteristics of the stimulus that cannot be separated into independent components. Direction selectivity in ferret visual cortex is not present at the time of eye opening, but instead develops in the days and weeks following eye opening in a process that requires visual experience with moving stimuli. Classic Hebbian or spike-timing-dependent modification of excitatory feed-forward synaptic inputs is unable to produce direction-selective cells from unselective or weakly directionally biased initial conditions because inputs eventually grow so strong that they can independently drive cortical neurons, violating the joint spatial-temporal activation requirement. Further, without some form of synaptic competition, cells cannot develop direction selectivity in response to training with bidirectional stimulation, as cells in ferret visual cortex do. We show that imposing a maximum LGN-to-cortex synaptic weight allows neurons to develop direction-selective responses that maintain the requirement for joint spatial and temporal activation. We demonstrate that a novel form of inhibitory plasticity, post-synaptic activity-dependent long term potentiation of inhibition (POSD-LTPi), which operates in the developing cortex at the time of eye opening, can provide synaptic competition and enables robust development of direction-selective receptive fields with unidirectional or bidirectional stimulation. We propose a general model of the development of spatiotemporal receptive fields that consists of 2 phases: an experience-independent establishment of initial biases, followed by an experience-dependent amplification or modification of these biases via correlation-based plasticity of excitatory inputs that compete against gradually increasing feed-forward inhibition. KEYWORDS: Feedforward, Hebbian, Reichardt detector, spatiotemporal, unsupervised PMID: 24598528 [PubMed - as supplied by publisher] END QUOTE Most ferret hunting happens in dark burrows, though polecats in some areas have frogs as a major dietary component, and other types of food sources typically found in crepuscular (low light) situations. Except for hunting done in darkness the visual ability discussed above is important for hunting, so this info might affect some choices in how BFFs or hunting ferrets are raised. There is still a lot being learned about ferret vision which disproves quite a bit of previous "general knowledge". For example, domestic ferrets have two types of cones, ones that are used to detect short wavelengths AND ones used to detect long wavelengths. Also, albinos have multiple visual shortfalls compared to ferrets with standard pelage. [Posted in FML 8061]