Scientists person agelong searched successful vain for a people of encephalon cells that could explicate the visceral flash of designation that we consciousness erstwhile we spot a precise acquainted face, similar that of our grandmothers. But the projected "grandmother neuron" -- a azygous compartment astatine the crossroads of sensory cognition and memory, susceptible of prioritizing an important look implicit the rabble -- remained elusive.
Now, newresearch reveals a people of neurons successful the brain's temporal rod portion that links look cognition to semipermanent memory. It's not rather the apocryphal grandma neuron -- alternatively than a azygous cell, it's a colonisation of cells that collectively remembers grandma's face. The findings, published successful Science, are the archetypal to explicate however our brains inculcate the faces of those we clasp dear.
"When I was coming up successful neuroscience, if you wanted to ridicule someone's statement you would disregard it arsenic 'just different grandma neuron' -- a hypothetical that could not exist," says Winrich Freiwald, prof of neurosciences and behaviour astatine The Rockefeller University.
"Now, successful an obscure and understudied country of the brain, we person recovered the closest happening to a grandma neuron: cells susceptible of linking look cognition to memory."
Have I seen that look before?
The thought of a grandma neuron archetypal showed up successful the 1960s arsenic a theoretical encephalon compartment that would codification for a specific, analyzable concept, each by itself. One neuron for the representation of one's grandmother, different to callback one's mother, and truthful on. At its heart, the conception of a one-to-one ratio betwixt encephalon cells and objects oregon concepts was an effort to tackle the enigma of however the encephalon combines what we spot with our semipermanent memories.
Scientists person since discovered plentifulness of sensory neurons that specialize successful processing facial information, and arsenic galore representation cells dedicated to storing information from idiosyncratic encounters. But a grandma neuron -- oregon adjacent a hybrid compartment susceptible of linking imaginativeness to representation -- ne'er emerged. "The anticipation is that we would person had this down by now," Freiwald says. "Far from it! We had nary wide cognition of wherever and however the encephalon processes acquainted faces."
Recently, Freiwald and colleagues discovered that a tiny country successful the brain's temporal rod portion whitethorn beryllium progressive successful facial recognition. So the squad utilized functional magnetic resonance imaging arsenic a usher to zoom successful connected the TP regions of 2 rhesus monkeys, and recorded the electrical signals of TP neurons arsenic the macaques watched images of acquainted faces (which they had seen in-person) and unfamiliar faces that they had lone seen virtually, connected a screen.
The squad recovered that neurons successful the TP portion were highly selective, responding to faces that the subjects had seen earlier much powerfully than unfamiliar ones. And the neurons were accelerated -- discriminating betwixt known and chartless faces instantly upon processing the image.
Interestingly, these cells responded threefold much powerfully to acquainted implicit unfamiliar faces adjacent though the subjects had successful information seen the unfamiliar faces galore times virtually, connected screens. "This whitethorn constituent to the value of knowing idiosyncratic successful person," says neuroscientist Sofia Landi, archetypal writer connected the paper. "Given the inclination nowadays to spell virtual, it is important to enactment that faces that we person seen connected a surface whitethorn not evoke the aforesaid neuronal enactment arsenic faces that we conscionable in-person."
A tapestry of grandmothers
The findings represent the archetypal grounds of a hybrid encephalon cell, not dissimilar the fabled grandma neuron. The cells of the TP portion behave similar sensory cells, with reliable and accelerated responses to ocular stimuli. But they besides enactment similar representation cells which respond lone to stimuli that the encephalon has seen earlier -- successful this case, acquainted individuals -- reflecting a alteration successful the encephalon arsenic a effect of past encounters. "They're these precise visual, precise sensory cells -- but similar representation cells," Freiwald says. "We person discovered a transportation betwixt the sensory and representation domains."
But the cells are not, strictly speaking, grandma neurons. Instead of 1 compartment coding for a azygous acquainted face, the cells of the TP portion look to enactment successful concert, arsenic a collective.
"It's a 'grandmother look area' of the brain," Freiwald says.
The find of the TP portion astatine the bosom of facial designation means that researchers tin soon commencement investigating however those cells encode acquainted faces. "We tin present inquire however this portion is connected to the different parts of the encephalon and what happens erstwhile a caller look appears," Freiwald asks. "And of course, we tin statesman exploring however it works successful the quality brain."
In the future, the findings whitethorn besides person objective implications for radical suffering from prosopagnosia, oregon look blindness, a socially isolating information that affects astir 1 percent of the population. "Face-blind radical often endure from depression. It tin beryllium debilitating, due to the fact that successful the worst cases they cannot adjacent admit adjacent relatives," Freiwald says.
"This find could 1 time assistance america devise strategies to assistance them."