<P> Haist, Gore, and Mao, sought to examine the temporal nature of consolidation within the hippocampus to test MTT against the standard view . They found that the hippocampus does not substantially contribute to the recollection of remote memories after a period of a few years . They claim that advances in the functional magnetic resonance imaging have allowed them to improve their distinction between the hippocampus and the entorhinal cortex which they claim is more enduring in its activation from remote memory retrieval . They also criticize the use of memories during testing which cannot be confirmed as accurate . Finally, they state that the initial interview in the scanner acted as an encoding event as such differences between recent and remote memories would be obscured . </P> <P> Nadel and Moscovitch argued that when studying the structures and systems involved in memory consolidation, semantic memory and episodic memory need to be distinguished as relying on two different memory systems . When episodic information is encoded there are semantic aspects of the memory that are encoded as well and this is proposed as an explanation of the varying gradients of memory loss seen in amnesic patients . Amnesic patients with hippocampal damage show traces of memories and this has been used as support for the standard model because it suggests that memories are retained apart from the hippocampal system . Nadel and Mocovitch argue that these retained memories have lost the richness of experience and exist as depersonalized events that have been semanticized over time . They suggest that this instead provides support for their notion that episodic memories rely significantly on the hippocampal system but semantic memories can be established elsewhere in the brain and survive hippocampal damage . </P> <P> Learning can be distinguished by two forms of knowledge: declarative and procedural . Declarative information includes the conscious recall of facts, episodes, and lists, and its storage typically connected with the MTL and the hippocampal systems as it includes the encoding of both semantic and episodic information of events . Procedural knowledge however has been said to function separate from this system as it relies primarily on motor areas of the brain . The implicit nature of procedural knowledge allows it to exist absent from the conscious awareness that the information is there . Amnesic patients have shown retained ability to be trained on tasks and exhibit learning without the subject being aware that the training had ever taken place . This introduces a dissociation between the two forms of memory and the fact that one form can exist absent the other suggests separate mechanisms are involved in consolidation . Squire has proposed the procedural knowledge is consolidated in some cases by the extrapyramidal motor system . Squire demonstrated that intact learning of certain motor, perceptual, and cognitive skills can be retained in patients with amnesia . They also retain the ability to be influenced by priming effects without the patients being able to consciously recall any training session occurring . </P> <P> The amygdala, specifically the basolateral region (BLA) is involved in the encoding of significant experiences and has been directly linked to memorable events . Extensive evidence suggests that stress hormones such as epinephrine play a critical role in consolidating new memories and this is why stressful memories are recalled vividly . Studies by Gold and van Buskirk provided initial evidence for this relationship when they showed that injections of epinephrine into subjects following a training period resulted in greater long - term retention of task related memories . This study also provided evidence that the level of epinephrine injected was related to the level of retention suggesting that the level of stress or emotionality of the memory plays a role on the level of retention . It is suggested that epinephrine affects memory consolidation by activating the amygdala and studies have shown that antagonism of beta - andrenoreceptors prior to injection of epinephrine will block the retention of memory effects seen previously . This is supported by the fact that beta - adrenoreceptor agonists have the opposite effect on the enhancement of memory consolidation . The BLA is thought to be actively involved in memory consolidation and is influenced strongly by stress hormones resulting in increased activation and as such increased memory retention . The BLA then projects to the hippocampus resulting in a strengthened memory . This relationship was studied by Packard and Chen who found that when glutamate was administered to the hippocampus, enhanced consolidation was seen during food - rewarded maze tasks . The opposite effect was also seen when the amygdala was inactivated using lidocane . Studies appear to suggest that the amygdala effects the consolidation of memories through its influence with stress hormones and the projections to other brain areas implicated in memory consolidation . </P>

When does consolidation of new memories primarily happen