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DTSTART:20260329T030000
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DTSTAMP:20260416T010041Z
UID:1764842400@ist.ac.at
DTSTART:20251204T110000
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DESCRIPTION:Speaker: Predrag Zivadinovic\nhosted by Paul Schanda\nAbstract:
  A major challenge in neuroscience is deciphering how the brain orchestrat
 es behavior in response to changes in environmental conditions. This proce
 ss is characterized by several processing stages\, from perception to the 
 storage of important information. Information storage is performed by a me
 mory system implemented through complex networks of highly interconnected 
 neurons. The collective operational principles of neuronal networks that s
 upport formation and storage are the main topics of this thesis.To investi
 gate the collective dynamics of the hippocampus from the perspective of th
 e brain criticality hypothesis\, I started by analyzing cascades of neural
  activity ¯ neuronal avalanches¯ that have been characterized by the abs
 ence of a typical spatial or temporal scale. Measures derived from neurona
 l avalanches suggested that during wakefulness the hippocampus operated fu
 rther away from criticality than during sleep/rest. In addition\, neural a
 ctivity propagated differently in these two brain states\, as indicated by
  different collapses of the avalanche shapes.Next\, the Phenomenological R
 enormalization Group approach also indicated conceptually similar differen
 ces\, through the scaling exponent of activity variance α\, which was hig
 her during sleep/rest than during awake. These results confirmed that the 
 activity of the hippocampus exhibits signatures of criticality and that th
 ese signatures change with the state of the brain.Next\, I found that memo
 ry retention was predicted by the scaling exponent of activity variance α
 . The exponent α measured during the sleep/rest session that followed lea
 rning correlated with memory retention during the subsequent unrewarded te
 sting session. Moreover\, α predicted performance even when controlled fo
 r reactivation that occurs in parallel. Second\, α measured in the sleep/
 rest phase that preceded learning was correlated with the learning speed.I
  analyzed distributions of the cells’ characteristic timescale and burst
 iness. The day-to-day variability of these distributions\, during sleep/re
 st that followed learning\, correlated with the scaling exponent of activi
 ty variance α\, as well as with memory retention. These findings confirme
 d that variance scaling and functional heterogeneity provide behaviorally 
 meaningful perspectives on hippocampal activity\, as they are directly rel
 ated to memory consolidation.I further investigated the process of memory 
 acquisition and consolidation between the hippocampus CA1 and the mEC. Dur
 ing learning\, CA1 cells shifted their firing field towards the goals\, wh
 ile mEC cells remained mostly stable\, shifting their firing fields toward
 s the goals during sleep/rest that followed learning. This shift during sl
 eep/rest was supported by the reactivation process\, which occurred in two
  ways\, synchronously with CA1 (during SWRs) and independently of the hipp
 ocampal SWRs. Both types of reactivation predicted subsequent memory reten
 tion\, as well as the amount of goal-related remapping. Again\, the day-to
 -day variability of the distribution of the cell timescales correlated wit
 h the goal-related remapping\, in CA1 during the learning session and in m
 EC during sleep/rest. These results suggest that in spatial navigation tas
 ks\, the functional responsibilities of CA1 and mEC change between learnin
 g and sleep/rest and that their function benefits from increased functiona
 l heterogeneity among cells.
LOCATION:Central Bldg / O1 / Mondi 2b (I01.O1.008) and Zoom\, ISTA
ORGANIZER:
SUMMARY:Predrag Zivadinovic: Thesis Defense: Scale-free activity as a basis
  for spatial learning and memory in the brain
URL:https://talks-calendar.ista.ac.at/events/6180
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