Conditioning and Learning Test 3 Circuits Part 1 7 14 15 Hippocampus Now we look at how memory related information is processed both specifically and generally and use this information to make testable hypotheses about the importance of brain regions for memory in animals The content of Experience matters to the brain due to our Multiple Memory Systems an overview o Complete understanding of memory can only be achieved by recognizing that the content of an experience is important is it exciting Is it new o Keep in mind there are no actual places in the brain b c it is a network of a bunch of neurological circuits fMRIs and similar equipment have not helped this confusion since a place lights up when used but there are no neurons that act in isolation o Memory is not ONE memories are segregated into distinct often overlapping regions The brain is vast according to their content Some examples Perceptual Semantic Episodic Declarative Spatial Emotional Action Habit We learned of these differences from research on HM o Our episodic memory is most powerful when formed expectations are not met we get new information about the world when we fail which makes the event memorable an expectation represents knowledge already present but w a failure we did not know it This tells you that you re about to learn something priming you to remember it better we have also seen this before so episodic memory has some things in common with other types HM s contribution to Memory Research o The multiple memory systems view came about with significance placed on the hipp Dr Millner HM s doctor was operating on the assumption that memory was just one big construct as many people thought at the time o The hippocampus itself is part of the limbic structures connectivity from this area can be ascending descending or intrinsic w in all based on position of other places that receive its input But before we go forward with what HM s injury showed us what exactly is the hippocampus We have looked at the modulation structures that connect to it but we haven t looked how it processes information o Input goes from cortex para hippocampal gyrus perirhinal cortex entorhinal cortex hipp Gateway We base hippocampus activity on the assumption that our experience of any given point in time space is associated with a unique pattern of cortical activity Everyone s immediate and current surroundings are different o What enters the hippocampus There is a convergence of cortical activity through neurons to form those experiences mentioned above The convergence of input is in two steps first to parahippocampal perirhinal cortex 1 then to entorhinal cortex where it converges again 2 The idea of convergent input suggests there is a poly modal association area to create associations between multiple senses for a composite signal The hippocampus as it receives input from across all of these cortical areas takes a snapshot of the cortical activity at that specific moment this contains info About time and place experience of the event sequences of events as well It s like a brain selfie going through time and space and periodically capturing info On the brain this comes into play later This part is used for integration and amplification of experiences The connectivity within provides the opportunity for further convergence of cortical activity or amplification of the snapshot information The progression is entorhinal cortex Dentate Gyrus CA1 Neurons We are not entirely sure of the function of this intrinsic connectivity The left and right hippocampus are also connected and share information back and forth o Internal intrinsic connectivity what s going on inside o So what information leaves the hippocampus Output connectivity is divergent projecting out to every area that originally funneled information in not only does the hipp capture the original experience it can actually recreate that unique pattern This finding suggests a mapped feedback of the poly modal input If this is really the case then it is less that the brain is remembering than re experiencing the previous cortical activity already seen in the original experience This ascending output recreates the selfie Episodic memory does this especially to reactivate the brain in a similar or the same pattern we seem to re live the experience that created that pattern o It is also useful to know that there are no connections from the hippocampus to the basal ganglia there are some descending circuits but not much is known These mostly go to areas that output to the hypothalamus for motivated behavior o SUMMARY of Hippocampus Activity Main input convergent poly modal sensory input from cortex and arousal info modulation signals Intrinsic additional integration or amplification Main Output Divergent back to the cortex for re activation and some descending down to the hypothalamus related areas And don t forget the input from the other side of the hippocampus Now back to HM s contribution to research o Everything we know about the brain and memory came from studies like this on patients with epilepsy that had medial temporal lobe bilaterally removed not just hippocampus but also amygdala and other necessary areas Animal Models of HM s amnesia o He suffered retrograde amnesia of episodic memory from this surgery not declarative or semantic as well as permanent anterograde amnesia Researchers started to think that memory deficit was possibly due to more than the removal of the hippocampus As such they needed a model to test the role of all structures in the surgery to see which ones could affect a loss of episodic memory connections from the hippocampus o Researchers gave HM a mirror tracing task over three days they saw that he could acquire new skills but could not remember learning those skills could not convert short term into long term declarative memory This was their first glimpse into different types of memory long vs short especially He was not the first to display a specific amnesia but what was unique was the location of his brain damage Specific regions may be critical to memory and researchers actually had a testable hypothesis about just what regions were critical SLIDES o To better look at the hypothesis and see what happened in HM to his episodic memory which part of the brain was needed We need an animal test of episodic memory sometimes progress is failing big and learning that things are more complicated than you thought Tried to use something called the delayed