Gating Mechanism

Bedeutung für EFs gemäß unity/diversity model

Bedeutung für Performance in konkreten Aufgaben

updating

common EF

shifting

Set-shifting task

n-back

AX-CPT

enthält Shifting und Common EF als latente Variablen

wahrscheinlich beeinflusst durch cortical signal-to-noise ratio,
which is probably affected by tonic extracellular DA levels in PFC (Herd et al., 2014)


BG decides which of the PFC representations are “gated” to be performed or remembered (learns the final gating decisions based on predictions of reward)
PFC creates representations of candidate actions, task sets, or memory items (learns these representations through error-driven mechanisms) (Herd et al., 2014)

laut Herd et al (2014) beeinflusst durch signal-to-noise ratio, nicht direkt durch den Gating Mechanismus

  • wahrscheinlich hat Gating keinen Einfluss auf den Shifting


    Faktor, da es hier um ungated, autmatic persistence von Repräsentationen geht:


  • uncontrolled (un-gated), automatic persistence of representations are good candidates for the Shifting-Specific component of EF .


  • Shifting-Specific component of the Unity/Diversity model may reflect the extent to which no-longer-relevant goals persist in PFC.




ability to actively maintain goals in the PFC layer and use those goals to bias processing in other brain areas (Herd et al 2014)

Neural factors:

  • several neural factors that contribute to a tendency to maintain information in PFC (regardless of the gating decision from BG) should contribute to worse switching performance

  • neural factors that are triggered by gating, but serve actively to clear out old representations


  • density and strength of recurrent connections within PFC

  • intrinsic tendency of neurons to fire persistently (hysteresis)
  • signal-to-noise ratio (gain) as influenced by dopamine and the COMT genetic variation, among others.
  • Signal-to-noise ratio should also be controlled by neural factors that affect active clearing of PFC representations with gating (as captured by the clearing on gating parameter).

alles Herd et al (2014)

this ability primarily involves the replacement of no-longer-active goals. We have explored two mechanisms that influence individual differences in this trait: recurrent connection strength in PFC, and the degree of clearing of old representations when gating occurs (clearing on gating = parameter affecting the degree to which representations “decay” once active maintenance is toggled off. Hängt allerdings eher mit GABA als mit DA zusammen).

strength of goal maintainance, which is defined as the core function of the common EF, is related to dopamine function in the cortex (Herd 2014)

stickiness of representations, which is defined as the core of shifting, is rather related to GABA (Herd 2014)


Working memory updating tasks require:

  • storing information
  • gating information into and out of working memory
  • tracking serial order (binding)
  • selective attention
    (Chatham et al., 2011)

enthält Updating und Common EF als latente Variablen

in computational models:

Go units correspond to the direct pathway of the striatum, and no-go units correspond to the indirect pathway. As such, go units have a disinhibitory effect on cortico-thalamic gating, thereby allowing working memory to be updated; no-go units have an inhibitory effect on cortico-thalamic gating, thereby helping to keep the contents of working memory the same despite new incoming information.

orientiert an medium spiny projection neuros of the striatal matrix (Chatham et al 2011)

Gating mechanismus: order specific gating signal in the striatum
--> ist einer von mehreren Mechanismen, die n-back Performance beeinflussen

recent lure errors arise from an instability of prefrontal activation states independent of gating: The clean separation between representations of items of different serial orders is corrupted on incorrect recent lure trials, both in terms of prefrontal activations and net input to prefrontal layers.


--> das heißt, dass zumindest die lure-Fehler in der nback eher durch Variablität in der Rubustheit von PFC Repräsentationen aufgetreten sind. Hier würde ich deshalb eine Parallele ziehen zu Herd et al. (2014), die zu Common EF sagen, es sei die "ability to actively maintain goals in the PFC layer" . Die lure-Fehler in der nback könnten somit auf den Common EF zurückgeführt werden.


Wenn man das ganze noch weiterdenkt, dann könnte man auch überlegen wie es mit den n+x Fehlern aussieht. Wenn man hier viele falsch-positive hat, würde das ja wahrscheinlich für eine besondere Robustheit von PFC Repräsentationen sprechen, die somit eine schlechtere Performance in der nback mit mehr Stabilität (im Sinne von Rigidität) in Verbindung bringen würde.