Friends and Grandmothers . Grandmother Cell refers to the notion that the brain has a separate neuron to detect and represent every object (including one's grandmother) · A more technical term for the grandmother cell is "sparseness" · At earlier stages in the brain's object-representation pathway, the neural code for an object is a broad activity pattern distributed across a population of neurons, each responsive to some discrete visual feature . · At later processing stages, neurons become increasingly selective for combinations of features5, and the code becomes increasingly sparse - that is, fewer neurons are activated by a given stimulus, although the code is still population-based . · Sparseness has its advantages, especially for memory, because compact coding maximizes total storage capacity, and some evidence suggests that sparsification is a defining goal of visual information processing · Grandmother cells are the theoretical limit of sparseness, where the representation of an object is reduced to a single neuron · Quiroga and colleagues recorded activity structures in the human medial temporal lobe that are associated with late-stage visual processing and long-term memory - This includes the entorhinal cortex, the parahippocampal gyrus, the amygdala, and the hippocampus; these recordings were made in the course to treat epilepsy - Findings of Jennifer Anniston and Halle Berry are in other article!
· The striking aspect of these results is the consistency of responses across different images of the same person or object. - This relates to the idea of invariance - One of the most difficult aspects of vision is that any given object must be recognizable from the front or side, in light or shadow, and so on. However, the brain consistently invokes the same set of memory associations that give the object meaning - According to View-Invariant Theories, this is achieved in the visual cortex by some kind of neural calculation that transforms the visual structure in · However, seeing as most of Jennifer Anniston's features overlap with those of Julia Roberts, you would think that there would would substantial overlap in the neural groups representing these two women, and cells responding to one but not the other would be rare. - The invariance demonstrated by Quiroga implies sparseness bordering on grandmotherness - However, the responses from these brain regions may be more memory-related than strictly visual; as several cells responded to not only photos but also the printed name of a particular person or object; thus this invariance must be based on learned associations as opposed to transformation of visual structure - Example: one neuron responded to Jennifer anniston and her Friends co-star Lisa Kudrow · The Quiroga findings say less about visual representation as such then they do about memory representation and how it relates to visual inputs