10/1 Identifying the engram for Non-specific/specific CR aquisition

Readings: Dudai Ch 11 pgs 166-176
other resources:

• Martinez & Kesner (1991) Learning and Memory a Biological View. Academic Press. Ch 9.
• Bear et al. (1996) Neuroscience: Exploring the Brain. Williams & Wilkins. pg 415

Notes:

I. Engram- Pathway that mediates the CR.

1. Ablations
2. Correlating electrophysiolgical activity with behavior.
• Language of neurons. FIG 1
• Seriality is assumed but not necessarily true.

II. Non-specific CR aquisition - change in central psychological state, arousal when positive reinforcers are used and fear when aversive reinforcers are used.

1. Responses.

• Galvanic skin response
• heart rate (bradycardia, tachycardia)
• pupillary dilation
• freezing
• blood pressure
• repiration

2. Conditioned heart rate in the pigeon

Setup

• box
• light (6sec)
• shock (.5sec)

Response

• UR changes heart rate from 150-190 to 300-450.
• CR increased heart rate 10 beats/min above baseline.

Aquisition FIG 2 

Pathway that conveys CS information. FIG 3

• Thalamofugal
• Principal Optic Nucleus (PON) of the Thalamus (analog of mamalian LGN).

CS presentation alone	US alone	CS  post training	repeated CS presentation without pairing.
60% increase firing rate	30% increase 30% decrease	no change enhanced response	no change or attenuation
40% decrease firing rate	20% increase 20% decrease	no change no change	attenuation

• Visual Wulst
• Tectofugal
• Optic Tectum
• Nucleus Rotundus

CS presentation alone	CS  post training	repeated CS presentation without pairing.
33% increase	increase	attenuation
66% decrease	no change	attenuation during initial trials

• Ectostriatum
  

CS presentation alone	CS  post training	repeated CS presentation without pairing.
20% no change	no change	no data
20 % increase discharge	enhancement	attenuation
60% decrease discharge	no change	attenuation during initial trials

• Pretectofugal
• Cetrifugal

Pathways that controls CR/UR.

• Autonomic nervous system FIG 4

Spinal Cord Thoracic/Lumbar levels	Vagus nucleus (X) located in the medulla
Sympathetic Ganglion (NE)	Parasymapthetic Ganglion (Ach)
Heart Rate

Pathways that convey US information. Heart rate is mediated by innervation of the heart. Response is not secondary to somatic, respiratory, or hormonal responses.

• Locus Coeruleus (NE)
1. LC sends direct projections to PON
2. Stimulation of LC alters firing rates of PON neurons ina manner similar to that observed in response to the footshock US
3. Foorshock increases the discharge rate of LC neruons.
4. The iontophoretic application of NE onto PON neurons decreases the ongoing activity of many PON neurons
5. Lesions of the LC eliminate US evoked decreases in teh discharge of PON neurons.
6. A light paired with stimulation of the LC (US) became a condtioned excitor of the heart rate response.

Other relevant structures

Archistriatum (avian homolog of the mammalian amygdala) - stimulation of this structure can stimulate heart rate.

II. Aquisition of Specific CRs.

1. Responses

• Limb flexion
• Eyepblink
• Potentiated startle

2. Conditioned Eyeblink in Cats

Setup

• cat
• steriotaxic
• CS tone - 60-70dB 1ms (louder click could elicit eyeblink on its own)
• US glabella tap

Response/Acquistion

• CR EMG from facial muscles orbicularis oculi (eye), levator oris (nose) onset latency 20msec
• CS-US 20-400msec apart every 10 seconds. 4-6 sessions of 150 pairings/day.
• UR latency 9msec

Information Flow- FIG 5

Tone	CochlearNucleus	Medial Geniculate	Midline and Suprasylvian cortex	Pericruciate Ctx.	Facial Nucleus	movement
13 msec				8msec

Changes in cortical circuit

Midline and Suprasylvian cortex- Cells in this region had a heterogeneous firing pattern. Only those whose firing rate increased in response to CS were studied. In those cells and neuronal firing rate increased after conditioning. Also, these neurons showed a decrease in the spike threshold.

Changes in motocortex. Cells in this region were heterogeneous. Those that responded maximally to the elicitation of the CR showed increased activity after condtioning. Also, the threshold for eliciting a muscular response by electrical micostimulation and spike threshold decreased. Glabella tap affected cortical cells projecting to the orbicularis oculi, whereas when airpuffs directed to the nose were used as a US the cells projecting to the levator oris muscle selectively increased their firing rate. Non-associative changes were also evident.

Changes in the cells of the facial nucleus. Spike threshold for both a paired and US alone group were decreased 1 week after training. However, after 4 weeks only the group were pairing occured showed a decrease.

Lesions: Lesion of the rostral cortex (motor) suppressed the CR but no the UR.

Acquistion is facilitated by stimulation of the hypothalamus.

Albert Borroni
last modified 10/1/9612:00pm