how many connections does the brain make in a human life time

[Peron]

I'm not sure if I post it here, but her I go.

 

I know there are about 60-80 billion neurons in the human brain, capable of making a trillion connections. But what I would like to know is how many connections are made during a human life time. How many connections are left unused at the end of my life?

[Ringer]

It's extremely variable. Dendrites can change connections and connection strength in a matter of minutes, even seconds. There is no set connection number in any brain. Also, if neuronal connections are not used they will be 'removed'.

[jimfaster]

man has about 100 billion brain cells. Although different neurons fire at different speeds, as a rough estimate, it is reasonable to consider that a neuron can fire about once every 5 milliseconds, or about 200 times per second. The number of cells, each neuron is connected to also varies, but as a rough estimate, it is fair to say that each neuron connects to 1000 other neurons-so every time a neuron fires, about 1000 other neurons get information about the shooting. If we multiply all these stars, we have 100 billion neurons X 200 shots per second 1000-X connections per firing = 20 million billion calculations per second.

[SMF]

The number of synaptic connections in the brain, while very large, is not a very useful statistic. A cortical pyramidal cell may receive 20K synapses, but they only have one axonal output. Synapses on the cell may have excitatory or inhibitory input and these inputs sum to create the action potential output of the cell. For some cells the output is an action potential or not, while others have a relatively constant action potential rate that is modulated by the sum of inputs. I find it useful to think of each neuron as an analog Boolean logic gate. It is easy to see how an AND, OR, NOT, and so on, decision can be represented by the output of a neuron. Neurons in which modulation of output frequency is regulated can also display logic decisions, but they are mostly observed in finely tuned sensory systems.

 

Each neuron as a simple decision maker can get complicated because of the analog component. Excitatory and inhibitory synaptic inputs to a neuron can vary in frequency, timing, and position on the cell. A higher action potential frequency of an excitatory input can overwhelm an inhibitory input (and the reverse). An excitatory input can be blocked if an inhibitory one occurs at the same time (and the reverse) but if, for example, the inhibitory one arrives just after the excitatory one there will be a short burst of output action potentials that is shut off and prevented for some time afterward (pulse generator?). There may be a large number of excitatory inputs to a cell via the terminal ends of its dendritic tree that can sum to create, or modulate, action potential output, but if there is inhibitory input very near, or on, the axon hillock (where action potentials are initiated) all of the excitatory inputs are negated.

 

And then there are interneurons that don’t produce action potentials. The brain she is not so simple. SM