PTSD Flashcards
Trace conditioning
A form of associative learning that can be induced by presenting a (CS) and an (US) following each other, but separated by a temporal gap
Flashbacks
A vivid experience in which you relive some aspects of a traumatic event or feel as if it is happening right now.
Hippocampus
Plays the essential role of the hippocampus in episodic memory and spatial representation.
Has a crucial role in tasks involving learning and remembering contexts.
Involves storing episodic memory
The part of the limbic system, and plays important role in the consolidation of information from short-term memory to long-term memory, and in spatial memory that enables navigation.
A key brain area involved in the regulation of the stress response, exerting negative feedback on the hypothalamic-pituitary-adrenal (HPA) axis. Errors to the hippocampus affects the stress regulation
HPA axis
Hypothalamic-pituitary-adrenal (HPA) axis is the system within the body responsible for the release of glucocorticoid stress hormones.
Glucocorticoid stress hormones
Stress hormones, cortisol in humans and corticosterone in rodents.
They feedback onto two types of receptors in the brain: the mineralocorticoid receptors (MR) and glucocorticoid receptors (GR),
These are highly expressed in limbic structures of the brain, including the hippocampus.
While hippocampal MR mediates the effects of glucocorticoids on the assessment of the stressor and initiation of the stress response,
GR acts in the consolidation of acquired information (de Kloet et al., 2005)
Activation of these receptors produces negative feedback to the HPA axis to surpass the production of glucocorticoids, terminating the stress. –> Errors in hippocampal functioning affect this.
Allocentric memory
Other-centred information
Special info independent of the location (based on salient features of the environment)
=> Allows to find the way for from different positions
Egocentric memory
Self-centred information
Spatial reference and spatial working memory
Spatial reference memory: The ability to learn a consistent, fixed response to a spatial stimulus, reflecting a constant association between that spatial location and an outcome (e.g. home or reliable water source). Depends on LONG-term memory.
Spatial working memory: The ability to maintain trial-specific information for a limited period of time so that spatial responses can be adapted from trial to trial. (e.g. remembering where you have just been so that you can adopt an efficient search strategy). Depends on SHORT-term memory
Context
Can be introspective (internal states) and extrospective (external environment)
Complex and multimodal representations are formed by binding constituent elements into a unified representation
Can be perceived as elemental (unique details) or conjunctiva (the whole)
-> many definitions of different broadness = can be hard to replication in laboratories + that is presented in lab as “context” can differ between research
Episodic memory
Includes temporally and spatially specific thoughts, feelings, events and sensory-perceptual details, capturing the “what, where and when” of personally experienced events.
Context bound
Stored in hippocampus
Semantic memory
Refers to our knowledge of the world (Tulving 2002)
Relevant across different contexts
Hippocampus dysregulations in PTSD
Hippocampus is also particularly vulnerable to the effects of stress
Elevated glucocorticoid concentrations contribute to stress-induced atrophy of the hippocampus
Neuroimaging studies report significant reductions in hippocampus and rostral anterior cingulate cortex in PTSD = prolonged PTSD may have cumulative adverse effects on hippocampal volume (Felmingham et al., 2009)
PTSD patients exhibit dysfunction of the HPA-axis with high levels of corticotropin-releasing hormone in the cerebrospinal fluid (Bremner et al., 1997) and low levels of cortisol in urine (Yehuda et al., 1995), indicating an enhanced HPA-axis feedback regulation
Special memory in general
Considered to be complex multimodal representations of the environment that comprise information from different sensory modalities
How does Radial Arm Maze work?
A maze with arms 6-12 ) radiating out from a central area like spokes on a wheel
SRM and SWM are assessed by reward in only certain arms and the same arm can be rewarded a couple of times.
Entering the arm with no reward counts as an SRM error.
1) During SRM acquisition: animals are prevented from making any SWM errors by closing off the access to an arm after it has been visited. Thus, animals can only enter each arm once during this first phase.
Mice are prevented from making SWM errors during the SRM acquisition phase.
2) In the second phase of the experiment, SRM and SWM are simultaneously assessed mice are no longer prevented from re-entering the same arm. Food rewards ARE NOT replaced during this trial. –> Rat needs to apply a win-shift strategy (that is when it ‘wins’ a reward it then has to ‘shift’ to a different choice to gain further reward) and thus remember which arms it has already visited. This provides a test of SWM.
PTSD and elemental and configural learning
PTSD seems to be following the elemental conditioning when it should be configural but due to impairments in the hippocampus the configural is not working properly (studies by Honey et al., 2014 and Iiardanova et al., 2011 and Bannerman et al., 2014)
