so when we talk about the hippocampus we're really talking about the hippocampal
formation and the hippocampal formation has three subdivisions there is the hippocampus
proper the dentate gyrus and the dentate gyrus is pictured here it's this toothy part and hence
the name dentate so it's the tooth part and then the subiculum which can't really be
seen in this cartoon but these three parts the hippocampus the dentate gyrus and the subiculum
all together form the hippocampal formation the hippocampus itself has been called cornu
ammonas or Amun's horn and so if you're ever reading papers about the hippocampus you may
see it referred to as C a meaning cornea ammonas or a Amun's horn and there are subdivisions even
within the the hippocampus there's CA 1 2 & 3 which are subdivisions of the hippocampus that
have different synaptic connections the afferent connections of the hippocampus so it's receiving
information from the amygdala so that's going in all parts of the sensory cortex are coming
in the cingulate gyrus that's on the medial surface of the brain is sending information
into the hippocampus as is the frontal cortex so almost every place is going to send information
to the hippocampus information flowing out of the hippocampus or efferent information is going to go
back to the amygdala back to the sensory cortex back to the frontal cortex it's also going to go
to the hypothalamus which is pictured here this is the mammillary nucleus of the hypothalamus
and it also sends information back to the anterior nucleus of the thalamus itself and
remember that the thalamus and the hypothalamus are part of the diencephalon I want to draw your
attention to a very important outflow from the hippocampus which is the fornix and that's this
big fibre tract pictured here and this fiber tract the fornix connects the hippocampus or
the hippocampal formation as a whole to the mammillary nucleus of the hypothalamus the
mammillary nucleus is important and I'm not exactly sure how it contributes to memory but
this reciprocal connection the connection to and from the mammillary nucleus and the
hippocampal formation is important and we know this because of a thing called Korsakov syndrome
this is a specific type of anterograde amnesia that results from a b6 deficiency so if you're
not getting enough vitamin b6 and they first noticed this in severe people with severe
alcoholism because they're their digestive system is not absorbing b6 or they're really
malnourished that this specifically has a deleterious effect on the mammillary
nucleus and that that mammillary nucleus the problems with mammillary nucleus in
turn results in an anterograde amnesia and when they did for their studies they found
that the mammillary nucleus was connected to the hippocampal formation so if you I think if
you you can recover from Korsakov amnesia if you start to eat right the circuitry of the of the
hippocampal formation is kind of complicated but not so terrible I'm not going to ask you
to memorize this but I do want to kind of give you an overview of how we think it works this
is called the perforin pathway okay and when we talked about the afferent connections into the
hippocampus we talked about all stuff coming from all of these multimodal sensory areas
they're all going to feed into an area called the internal cortex so if we have the campus
just outside is our temporal lobe so if our temporal cortex is kind of out here all of this
information is coming into the internal cortex which is part of our temporal lobe from there
it goes into the dentate gyrus from the dentate gyrus it goes into the hippocampus proper the
ca3 and ca1 just that general hippocampus area then it goes from the hippocampus to the simba
kuelen again these are all three layer 2 camp 3 layered cortex and then from these two areas the
information goes back out to the multimodal multi-sensory Association cortex so it's a
loop the more you study neuroscience and then especially when you start to talk about behavior
and behavioral systems motor sensory limbic all of these things you're going to find that they're all
loops great big circular or oblong loops that are taking information from one area processing it and
sending it back out to where it came from I simply want to introduce this because as you go through
your studies of neuroscience you will probably run into the perforin pathway and now at least
it will ring a bell when you have a more detailed lecture on it so now that you have seen the
perforin pathway the next time you run across it when you're taking in a more advanced neuroscience
course you'll be familiar with the terminology and the different parts of the perforin pathway