Quoted by Dr. X:
Anatomists have found that in most areas of the cortex, for every fiber carrying information up the hierarchy, there are as many as ten fibers carrying processed information back down the hierarchy...
Ten times as many going "down" than "up"? I find it fascinating that there are such identifiable anatomical structures which correlate with what we know well: perception is not "input." It's our brain and mind's interaction with the input not just in the cortex where we expect processing and interpretation to take place, but also back down to the sensory level itself.
So sensation itself is not passive reception: it is shaped by the cortex. Another quote:
[Y]our understanding of reality is a far cry from reality itself. Your understanding of reality is constructed in large part according to your expectations and beliefs, which are based on all your past experiences which are held in the cortex as predictive memory. This is worth repeating: Many of your perceptions—what you see, hear, feel, and think is real—are profoundly shaped and influenced by your beliefs and expectations.
I think it's a big leap from the micro-anatomy of basic sensory perception to the theme of construction of reality, but it's always a good topic. The piece is further quoted and linked here.
Photo: A stained cortical neuron in a sea of dendrites
