Verborgen vertraging: hoe hersenen in Multiple Sclerose informatieverwerking beïnvloeden
Niet iedereen verwerkt informatie even snel. We staan daar niet bij stil, maar mensen met vertraagde informatieverwerking hebben meer moeite met het uitvoeren van alledaagse activiteiten. Het meest opvallend aan mensen met Multiple Sclerose (MS) zijn de zichtbare fysieke beperkingen. Maar wist je dat mensen met MS vaak last hebben van cognitieve beperkingen, waaronder vertraagde informatieverwerking?
Door het bestuderen van magnetische hersenactiviteit kon ingenieursstudent Olivier Burta achterhalen hoe de snelheid van informatieverwerking eigenlijk tot stand komt. Deze hersenactiviteit was opgemeten bij mensen met MS gedurende een cognitieve test, die routinematig in de kliniek wordt gebruikt. Ben je benieuwd hoe MS de snelheid van informatieverwerking concreet kan beïnvloeden, of wil je weten op welke manier dit werk kan bijdragen tot toekomstige MS behandelingen? Blijf dan zeker verder lezen!
Levenslange beperkingen
Multiple sclerose (MS) is een ingewikkelde auto-immuunziekte met hersenschade als gevolg. Deze littekens kunnen zich vrijwel overal in het centrale zenuwenstelsel (hersenen en ruggenmerg) vormen, waardoor de mogelijke klachten heel divers zijn. Zo kan de ene persoon met MS spierzwakte ondervinden, terwijl een andere geheugenstoornissen ervaart. En dat laatste is belangrijk, aangezien de meesten onder ons een verkeerd beeld hebben over deze ziekte: “MS is een spierziekte en je belandt sowieso in een rolstoel.” Maar de cognitieve achteruitgang is minstens even belangrijk en mag absoluut niet worden verwaarloosd.
Cognitie omvat alles wat betreft kennis en informatie. Het verwerven, verwerken, onthouden en toepassen van informatie vallen allemaal onder deze noemer. Hoewel verschillende aspecten van cognitie aangetast zijn bij MS, staat één daarvan centraal: de snelheid van informatieverwerking. Stel dat je als persoon met MS een familiebijeenkomst organiseert. Het plannen van zo’n evenement vraagt om veel taken die elkaar snel opvolgen. Wanneer bij elke taak vertraging optreedt, stapelt dit zich op en kan het ervoor zorgen dat niet alles op tijd af is. Dit kan ook bijdragen tot extra stress en vermoeidheid. Bovendien is MS een levenslange ziekte die jongvolwassenen voor aanzienlijke uitdagingen kan stellen. Tegenwoordig zijn er maar zeer beperkte behandelingen die een effect hebben op cognitie, maar we kunnen MS nog niet genezen.
Hoe wordt die snelheid gemeten?
Om te bepalen in hoeverre informatieverwerking vertraagd is, wordt standaard een neuropsychologisch onderzoek (NPO) uitgevoerd. De meest gebruikte test is de Symbol Digit Modalities Test (SDMT). Het doel is om een rij symbolen om te zetten naar cijfers van 1 tot 9. De correcte antwoordkeuze bij elk symbool kan je in een legenda raadplegen. Hoe hoger het aantal correcte antwoorden binnen 90 seconden, hoe beter de SDMT score. In het algemeen zal een persoon met MS een lagere score behalen in vergelijking met een klinisch gezonde persoon.
Ondanks de hoge gevoeligheid van deze test voor het vaststellen van vertraagde informatieverwerking, blijven er na afloop nog veel vragen onbeantwoord, zoals: “Wat vertelt dit over de mogelijke oorzaken van mijn vertraagde informatieverwerking?” of “Wanneer loopt er iets fout als ik inkomende informatie verwerk?” Voor dit soort details moeten we verder gaan kijken. De oplossing? Laten we ons richten op de hersenen en hun activiteit, want het is juist daar dat alle cognitieve processen tot stand komen.
Onze hersenen liegen nooit
In dit thesisonderzoek werd de breinactiviteit van personen met MS gemeten terwijl ze de SDMT uitvoeren. Deze activiteit bestaat uit elektrische signalen die worden opgewekt in specifieke delen van je hersenen, afhankelijk van de veranderingen in je omgeving. Stel dat je plotseling iets ziet verschijnen. In eerste instantie zullen je ogen deze informatie oppikken en verder doorgeven. Hierna wordt de occipitale kwab geactiveerd, het deel van de hersenen dat zich helemaal aan de achterkant bevindt. Het meten van deze elektromagnetische velden stelt ons in staat gegevens aan zeer hoge tijdsresolutie vast te leggen. Cognitie ontwikkelt zich over enkele milliseconden, waardoor deze aanpak optimaal is!
Dankzij een methode gebaseerd op artificiële intelligentie (AI), konden we achterhalen hoeveel hersennetwerken activeren gedurende de SDMT. Een hersennetwerk is een groep regio’s in de hersenen die samenwerken om informatie te verwerken. Bovendien is elk verkregen netwerk gekenmerkt op 3 vlakken: in de tijd, in de ruimte, en in het frequentiedomein. Zeer gedetailleerd dus, wat ons nieuwe inzichten biedt.
3 factoren vormen een geheel
In totaal hebben we 4 unieke hersennetwerken geïdentificeerd. Bij elke nieuwe visuele stimulus gedurende de SDMT, activeren deze 4 netwerken in chronologische volgorde. Door het bestuderen van de kenmerken in elk netwerk, konden we deze verdelen onder 3 groepen: sensorische, cognitieve, en motorische snelheid. Dit betekent dat de snelheid van informatieverwerking moet worden gezien als de som van deze 3 factoren. Deze nieuwe beschrijving markeert een doorbraak in ons begrip van hoe de snelheid van informatieverwerking wordt geëvalueerd met de klinische SDMT test. Bij een psycholoog ligt de focus op het bepalen van de cognitieve snelheid van een patiënt. Om dit te bereiken, moeten dus zowel de sensorische als de motorische snelheid op een uiterst nauwkeurige manier worden bepaald.
Verder waren we in staat te ontdekken welke netwerken verstoord zijn bij mensen met MS. De correcte werking van het eerste en tweede netwerk, verantwoordelijk voor respectievelijk stimulusperceptie en uitvoerende functies, wordt aangetast door MS. Deze kennis kan worden gebruikt om toekomstige behandelingen voor MS te ontwerpen. Enerzijds kan dezelfde analysemethode worden gebruikt om de effecten van cognitieve revalidatie op te volgen. Anderzijds kan deze studie aanleiding geven tot meer gerichte neurostimulatie, waarbij de focus ligt op het herstellen van de integriteit in één van de hersennetwerken. Bij neurostimulatie worden de hersenen gestimuleerd aan de hand van externe elektrische stromen, wat in dit geval kan leiden tot een verbeterde snelheid van informatieverwerking. Dit allemaal heeft één overkoepelend doel: het verbeteren van de levenskwaliteit van mensen met MS die te maken hebben met cognitieve beperkingen.
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